This is hands down the best concealer I've tried for covering up blemishes. It does not work underneath my eyes though, but that's only because my skin there is too thin and dry.
I use a NC20 which is really close to my skin colour, but if you have porcelain or ebony skin, it will probably be difficult to find one that suits you.
It also has spf 35 in it, but it does not reflect light and it offers a great amount of coverage. If you are looking for something sheer, you may want to choose another one.
The only negative thing I have to say about this is that it's not cruelty free, which is the main reason why I'm not gonna repurchase this product.

can't remember if I had this or the pro longwear - either way undoubtedly the best concealer I've tried. Unfortunately I keep losing them so will definitely be picking one up at the airport next week. No concealer I've tried has the staying power and there's no oily residue like my current temporary Rimmel coverstick. To be honest, this product is definitely worth the price, and if I'm getting it at the MAC store or the duty free, I always make note to get matched then buy the lighter shade. (I like to pick one that's a little lighter than my skin tone to brighten up underneath my eyes.)

I love this concealer! At first I wasn't really sold on the form of the concealer, but I find it really good because it's pretty creamy like and easy to apply! The solid form of this concealer actually helps me to stay pretty matte during the day and gives a good coverage of unperfections.

After 14 years of using it on and off, I won't say it's perfect (which concealer is?) but it definitely works for my skin.

I have normal/combi skin and am past the age where blemishes and looking super-matte are a major priority. I prefer something that is flexible to use (opaque or sheer as I please), and LOOKS like real skin, while correcting skin tone and dark circles or the odd blemish or two.

Studiofinish has a waxy texture that is thick and dry when cool, but softens and emulsifies when warmed. I can apply it thick, then easily sheer it out where needed. It isn’t powdery and doesn't set, so the texture stays skin-like and oh-so discreet while providing coverage. If you use the right shade and don't set it with powder it looks like you have no makeup on. I also love that they have different undertones as I like using NW for dark circles and NC/C for any dark or red spots. Not the cheapest or the most expensive, but one pot lasts forever because you don't need much, and it doesn't separate and go bad like tube concealers can.

It’s not perfect; if you’re very oily and/or acne-prone, it can slide off because it doesn't set. (In general pot products also aren't a good idea for acnegenic skins because you can contaminate the product if you double-dip your brush or finger after touching your skin.) If you are very dry or you're using this in a cold climate, you also need to make sure you moisturize well beforehand, or the product is hard to blend out.

Will probably keep buying for a long time!

I've used this product for almost an entire year. It has high coverage but can get cakey very easily. I do like this product and it does last for a long time but don't use if you have dry skin. I have a lot of patches and dry skin on my forehead and and nose so when I apply this it looks worse since the product is thick. I would recommended the prolong wear concealer which I'm currently using because since its a liquid it doesn't make it as noticeable. It is a bit light for me (NC20) which is weird since in the prolong wear one NC20 is a bit darker but that's because I bought it in the dead of winter.
Either way I like the product, I've used it for a long time, has great coverage but I would mainly recommend this to people with oily to combination skin. I would also not repurchase.

Pros
Has high coverage
Lasts for a long time
Stays on skin for a long time

Cons
Gets cakey quickly
Makes dry skin look worse
Not too easy to blend

The one concealer for me! It actually conceals the dark circles under my eyes, has a lovely, creamy texture, and doesn't dry out the skin. Makes me look less tired immediately. I can be a lazy person makeup-wise, but I honestly say this is the only product I put on my face everyday.

Practical, small packaging. I apply it with a brush but it is also a nice concealer to take with you (camping, sleeping over, etc) and you can easily apply it with your finger if you don't have a brush by hand. It is best to put some powder over it because it can be a bit shiny, plus then it stays in place longer.

When I bought it I thought it was quite pricey, but a little goes a long way! I've bought mine definitely more than a year ago and it is still half full. For a top brand it's affordable, and for the quality you get it's worth paying a little more than I usually would.

Good: conceals perfectly, nice texture, price/quality
Bad: can be a bit shiny, sometimes it creases a little (so you need to put some powder over it)

I can recommend it to everyone.

A MAC artist recommended that I purchase this concealer to cover up my blemishes when I stopped by the counter yesterday. I will give this product credit where credit is due: it provides great coverage and lasts throughout the day. However, it settled into my dry areas and intensified two cystic blemishes I applied this concealer over. Also, NW15 was too light for me, even though I'm very fair skinned. This product is definitely too thick to use under the eyes, so please shy away from using it on that area of the face. If you're interested in purchasing a MAC concealer I recommend Select Moisturecover over Studio Finish. It is a more versatile product.

A concealer that actually conceals. I have Clinique Advanced and Shiseido Natural Finish concealers but MAC SF is the only one I really use. It's heavy and a bit greasy but it doesn't make me break out or aggravate any hormonal cysts I may be covering (ahem Clinique). I know concealer should be applied under foundation but I conceal on top of my foundation, as it seems to stay in place better for me this way (even with face primer). I was matched at the MAC counter to NC30 back in the summer, and though I've gotten a bit paler it still blends right in.
I took off a lippie because the packaging (a flip-open pot like their eyeshadows) is not very hygenic but that's probably the best way to keep it (it's quite thick in consistenty). I take a bit out with a qtip so I'm not putting my concealer brush directly in the pot and possibly contaminating it. A little goes a long way, and I blend out around the blemish with a soft brush. Set with MUFE HD Powder and it stays all day. A decent price (around $15 USD) and it will last a long time. My HG concealer that I'd absolutely repurchase.

I had a huge, visible bruise right on my forehead which I got a few days before my Bat-Mitzvah and didn't seem to be going away. So I went to the MAC counter at Nordstroms and the lady put this on my bruise (along with the studio fix powder, which didnt do a whole lot) and it disappeared. It has GREAT coverage, but it's kinda annoying to apply and blend in a pinch. It works really well under the eye, too, but not the best at concealing the redness around my nose. It's not really an everyday concealer. Ever since it completely saved my butt on my Bat-Mitzvah I have fallen in love with it and am now always going to count on it. GREAT concealer, but it's expensive. Glad I wasn't the one paying.

NW10-15 (neutral-cool toned, very fair), blue eyes, Color season is True Summer, Baumann Skin Type is OSPW.

I own this product in the shade NW15. For light makeup days, or days I need to get out the door fast, I really like to use this as "foundation."

I spray MAC Fix+ on my counter, dab some onto my kabuki concealer brush (Ecotools limited edition), swirl into the Studio Finish concealer to pick up some product, and then just lightly dab all over my acne scarring on my cheeks. Then I blend the concealer into my skin, and it creates a very natural cover up and finish. I do the same for my under eye circles. Add a quick dash of setting powder and swipe of bronzer, and out the door!

the nice part is, this concealer seems to be lighter than other formulas of foundation or concealer that are NW15, so it blends into my skin, especially when applied with the Mac Fix + spray.

It lasts a long time, especially if sealed in with powder. Does not settle into lines once you blend in. If you don't take the time to blend while you are applying, it may be applied too thick and will settle into lines later on in the day.

Overall, not the perfect "covers any flaws and looks like skin" concealer, but it's my "HG runner-up".

EDIT: After wearing this a couple times, I am unimpressed with how much this slides around after application. It settles in my under eye lines, and it comes off my acne scarring really easily. : (