Update: I'm allergic to something in this. If I get it anywhere near my eyes, they swell and get irritated. I'm still using it (applying carefully) but boo!
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I like this stuff reasonably well. I haven't had any problems with it leaving a white cast on my face (certainly nothing in comparison with, for instance, the Chanel primer I tried last week, which isn't even a sunscreen) and it stays on well, in comparison to my previous regular player, the Cliniderm Gentle. I think I'd probably actually give this more of a 3.5 -- it's close, but I'm not in love with it.
The good:
Thin formulation spreads easily, I don't have to use much to cover my entire face (which is good, considering the high price for my tiny bottle)
Dries well, doesn't peel or rub off on clothes as far as I can tell
No skin reactions, allergies or breakouts
The not-so-great:
It has a weird smell -- very faint, and it fades shortly after application -- but plasticky with maybe a hint of floral? Barbie's makeup bag? I don't know.
Dries shiny. Not that this is anything weird; the only sunscreen so far that I've tried that didn't was the Lise Watier, and that one made me break out.
The bottle sucks rocks. It's skinny-based and unstable and if it tips over it goes on a wild spinny flight through the bathroom. The tiny little spout opening means you don't lose much product in the adventure, but it's still annoying.
Expensive (almost fifty dollars with tax when I bought it) and hard to find (only sold by one place anywhere close to me).

Hubby and I wore this before a walk ... we looked like extras in the Twilight cast.
Blended, rubbed - I even put makeup powder on top. This stuff has a heavy white cast. Kinda heavy/greasy going on but then sets and is white and doesn't move. Matte, slightly powdery finish.
At the end of the day, my skin had some dry flaky spots -- moisture sucked dry -- so I'm thinking this would be great for oily skinned folks.
Apparently, it's a good idea to use a moisturizer, and/or primer with this ... sheesh -- way too much stuff on my skin. In the summer, I like to limit my routine to serum, bit of concealer, spf and a touch of bronzer.
Teeny bottle. Add to that - Skinceuticals tests on animals :-(
Too many negatives for me. For an Spf 50 - I'll stick to Sheseido.

Oh boy! I am totally cheesed off. I both this from my derm doctor and have fallen in love with it. Great for my oily skin. No breakouts and very little skin aggravation and clogging. THEN I read the previous postings and found out that Skinceuticals is owned by L'Oreal - the dreaded company that does very cruel animal testing. Sadly, won't be repurchasing and would not suggest anyone else get it due to the animal testing L'Oreal does. So my rating is 1 (it doesn't allow a zero). L'Oreal and Skinceuticals, you should know better!

This is hands down the best sunscreen product I've ever used. I found it while shopping during a very bright hot day last summer and decided to get it and apply it on my skin before hitting the street again. It is much more liquid than most sunscreens in the market, so it goes on smoothly, evenly and dries a little powdery, so you don't get that sticky feel typical of many good sunscreens. It never makes my skin feel greasy, even in the summer, and I can layer it on without feeling it's caked on my face. Two drawbacks: it's very costly at $30 for less than 2 oz. (ouch!), and it's hard to find in stores where I live (mostly dermatologists carry it), so I have to order online and that might mean waiting a few days between bottles.

I tried using this sunscreen for almost a year and will not repurchase for two reasons:
Leaves a white cast/sickly effect on my NW15-20 skin;
Flakes horribly on random dry spots on my combination skin (even highlights dryness I couldn't see prior to application)
The positive aspects of this sunscreen include being very sheer and lightweight and also providing very good sun protection. The product wasn't worth the extra effort I had to make in order for it to work: adding color to counteract the sickly effect and using extra moisturizer to balance the dry spots (which made my skin feel too heavy and then negated the desire for a lighter-weight sunscreen).

I was disappointed in this. This provides decent suncreen protection and dries down to a soft, matte finish, but the tint is worse than Elta MD 41 tint, more ashy in color. I'm over these one tint fits all. I'll probally send this back and try Stila's new Illuminating SPF20 tinted moisturizer. If, Stila's doesn't work, I give up on tinted moisturizers.

This is the best and most cosmetically elegant sunscreen I have ever used. After washing my face with Cerave hydrating cleanser I apply my Nia 24 skin strengthening complex. After about 5 minutes I shake the skinceuticals and put small drops on the top of my hand and then apply to my face a small area at a time. It is so great that I even use it as a primer if I am not going to be out in the sun. Over this I use Bobbie Brown tinted moisturizer in extra light. My dry as desert skin is soft, smooth and well hydrated and looks great.

This is the absolute best sunscreen for my sensitive skin. In the past I used Clarins UV Plus HP Multi-Protection Dayscreen SPF 40, which worked really well for a few years. But my skin developed a sensitivity to it and it began causing irritation and reactions. Then most recently I used BurnOut Eco-Sensitive Zinc Oxide Sunscreen SPF 32 and though it never caused any issues on my skin, it isn't cosmetically elegant and felt a little too thick. So I'm thrilled to have found a sunscreen that has a similar texture and finish of the Clarins sunscreen I loved so much but without the unnecessary fragrance.

This is lightweight, watery, silky, and feels like I'm wearing nothing on my skin. The liquid consistency is almost exactly the same as the Clarins version but with a less greasy slip. This feels more watery and has a very slight grit to it as well. Not a sandy-grit or anything, more of a very fine dust-like texture hidden within all the liquid. It doesn't effect the smooth application or appearance once on the skin. It is a semi-opaque white color but it dries completely translucent and is undetectable on my skin.

I use about six or seven full drops and mix it with my moisturizer before I apply it on my face. I use another ten or so drops for my entire neck (I use a separate sunscreen for my chest and body). I like applying it that way to minimize the chance for uneven sunscreen distribution, and to minimize the potential for a white cast. Physical sunscreens tend to leave me with a white cast more often than not, but this one does not. However, if I use too much of this sunscreen or apply it over my moisturizer when it has already set into my skin, I do get a bit of a white cast.

I haven't ever burned while wearing this, and I love the SPF 50. I feel more secure with the high level of SPF and the fact that it's a physical sunscreen with both Titanium Dioxide and Zinc Oxide. It doesn't cause oiliness or dryness. No breakouts, irritation, or sensitivity. Makeup applies over this perfectly.

The 50mL bottle is substantial and sleek with a secure screw-top lid. The tiny dispenser prevents spillage and controls the amount needed. I can't recommend this enough and I'll definitely repurchase.

I love this! I'm very pale and sensitive to the sun and always looking for good products with SPF, and this is the best. Just a hint of colour and coverage, and I love the SPF factor. I put it on every morning after my morning skincare routine and it sinks in and leaves a matte finish - terrific!

I love this product b.c it is matte and I have sensitive, oily / combo skin that can get aggravated from other sunscreens. I make sacrafices in other categories of health/beauty (such as forgoing manis/pedis) so that I can afford to spend more on quality skin care products that are more investments in long term health.
I wear a drug store (Neutrogena) sunscreen as my daily sunscreen, but before exercising outside or when I'm going to be out for long periods of times, I will opt for this.
I know this should lose potency over time, but I still reach for this a year after purchasing it. If I start to notice that I'm getting tan or feeling the sun's rays, I'll have to toss.
This is one of the only sun screens not to break me out. And I wore it hiking through the desert when I didn't have access to running water to properly remove it before sleeping.

I was looking for a physical sunblock after reading about the disadvantages of chemical sunscreens, and ended up with this. It's not a holy grail, but it is extremely serviceable. There's a faint floral scent, which I do not like in skin care products, and the texture is slippery and fluid like the Anthelios sunscreens. Unlike Anthelios, however, the texture is a tiny bit gritty and there is, as other people have pointed out, a bit of a white cast left over after application, especially if you apply enough to get proper skin protection. I like that this leaves a slight matte effect and I'm pretty pale, so the white cast doesn't really bother me. It makes a great foundation primer. The bottle seems tiny for the price -- 50 ml for $30! -- but the paranoia-freak in me wins out, and rationalizes away the price in favor of the excellent protection and paraben-free formula.

I'm religious about sun protection and have been using this product for the past 6 month in lieu of my usual Cosmedix Reflect SPF 30 spray block. I hate any sticky greasy feeling on my face/neck so it's imperative to find a physical block that offers maximum UVA/UVB protection which dries invisible without a tacky feel. Having been through many sunblock brands in the past and all of Neutrogena's sunblock line for face and body (even the ones for babies), I will only ever use them now for my body; most sunblocks are either ineffective or breaks me out after a couple of hours on my face and I have to wash it off immediately after any physical activity where I perspire a little.
The texture of the Skinceuticals Sheer block is thicker than Cosmedix Reflect but still doable as a spray for layering over moisturizer as part of the AM routine. I apply it generously on my exposed skin, let it sink in before applying makeup and wait 15-20 minutes before walking out the door. My face is normally pretty oily in the t zone but this worked well to mattify me for 3-4 hours before having to blot. Recently I went on a trip for a month through SE Asia and carried this with me for my face and neck. Through some of the most aggravating mucky weather conditions for sun sensitive skin that's prone to breakouts, it performed wondrously. In and out of salt water, under the sun for 10+ hours a day, sweating buckets, through reapplication after reapplication, I didn't break out and didn't get burned. I still love my Cosmedix Reflect for the normal work day but this will be in my bag from now on.

My husband and I both love this! It doesn't congest our pores, feel sticky in anyway, or break us out! It is literally the perfect sunblock for us both!

I have a confession to make: I don't actually use this as a sunblock (though that's a great side bonus). I use this as a makeup primer/oil control product, and I really love it. Unlike what seems to be 99.9% of consumer, I am unable to use those silicone-based mattifyers that everyone loves. They just make me shinier. I work for a division of L'Oreal (which owns SkinCeuticals), so when I heard about this, I had to give it a shot. The matte effect lasts far longer than what I was using before, and I get to pat myself on the back for using sunblock. Of course, I would have a hard time paying $30 for less than 2 ounces if I weren't getting it for free, but the stuff is good enough that I would probably cave and do it. I think the packaging is fine, and I actually PREFER the screw top. I don't know how many times I have found a mess due to a flip-top sunblock leaking out. The smell IS kind of icky (like motor oil), but I prefer that to having a ton of artificial fragrance added in. All in all, a winner

not hg, but this is the closest to it. It doesnt irritate my skin, especially on my neck like the neutrogena one did, and didn't break me out like the shiseido sunblock did.
pretty good overall, especially since it's the first sun block that hasn't caused any problems with my skin.
edit:
caused me to break out... in cystic acne. I'm so sad that I had to stop using this :(

MedSpa sold me this sunscreen. They advise to use a bottle per month. After shaking vigorously, it's too watery to handle easily. Hard to get exact amount you want. Left a visible white coating on my face after 20 minute wait to sink in. It's greasy feeling and shows through makeup. My go-to mineral powder makeup looks like you put on a coat of thick foundation over this sunscreen. The bottle isn't stable to stand up & there's risk of spilling it all out. I'm under-impressed for price. Will go back to drugstore clear zinc brands. If you read literature about sunscreens, latest findings are that over 30SPF really does little more to help. continued >>

This is a great product for oily skin - truly goes on matte and feels like you are not wearing sunscreen. It is on the expensive side but I've found you only need a small amount to cover a large area. As far as the white cast, it does have that at first when you put it but then disappears after you rub it in. I have tan Indian skin and have no problem with the white cast! Definitely a winner!

If you are very oily and looking for a product that truly makes your foundation last and keeps you matte, this will absolutely do that. It TOTALLY delivers. However (you knew that was coming) it is not sheer. Not at all. It leaves a very obvious white cast and I don't know how anyone but the very fair could wear this. I am fair in the winter, and I'll keep this around for days when I need my makeup to last, but I am a stay at home mom and generally that doesn't apply to me. I don't use this on the beach even though it is seriously waterproof (you need an oil cleanser to remove it) and I don't lie on the beach, I swim, but I look so ghostly, sickly white. So this gets a low review from me for not being as advertised, a sheer physical block. The other reviewers accurately describe consistency and packaging.

breaks me out, cant be put under acne medication, DOES NOT COME OFF. EVER. its just not worth it at all sorry skinceuticals try again

I had high hopes for this. It was drying on the skin and made my make up look dry. It seemed to leave white dots on the skin as stated by previous users. Unsure of what to make of this product. Oh and by the way, that plankton (artemia extract) that is supposed to be so helpful to the skin; it is like the last ingredient listed on the package :( Guess it can't be too helpful in trace amounts.
SkinCeuticals Sheer Physical UV Defense SPF 50 ingredients:
Active ingredients:
Zinc oxide, titanium dioxide.
Other ingredients:
Water, isododecane, c-12-15 alkyl benzoate, undecane, triethylhexanoin, isohexadecane, nylon-12, caprylyl methicone, butyloctyl salicylate, phenethyl benoate, styrene/acrylates copolymer, silica, tridecane, dicaprylyl carbonate, dicaprylyl ether, talc, dimethicone/peg-10/15 crosspolymer, aluminium stearate, pentylene glycol, peg-9 polydimethylsiloxyethyl dimethicone, alumina, polyhydroxystearic acid, phenoxyethanol, magnesium sulfate, caprylyl glycol, peg-8 laurate, disteardimonium hectorite, tocopherol, propylene carbonate, artemia extract, benzoic acid, peg-9, D41547/1.