This is an expensive, "luxury" powder "sunscreen" sold at the offices of many dermatologists, especially ones who treat women concerned with anti-aging and dark spots/melasma. Everyone agrees that despite the company's claims that you can use this as a standalone sunscreen, you should apply a liquid or cream broad-spectrum sunscreen SPF30 or higher in the morning, and possibly use the powder for subsequent reapplications throughout the day. I am returning this product because it made me break out, which is a deal breaker, and I will detail more below.
I have used a slightly less expensive dupe called Brush On Block before, and I think that it was better than Colorescience. The Brush On Block had a nicer, softer brush and I had a much better experience with it, ie no breakouts. FYI, one Brush on Block ($32 for .12 oz) contains half the product and charges about half the price of Colorescience ($65 for .21 oz). But if you buy the set of 2 BoB ("Duo" is $54 for .24 oz), it ends up being over $10 less than CS. And I thought BoB only came in one shade but I just checked and see it comes in 2. I'm adding a separate review on the Brush on Block right now.
Here are the pros and cons of CS:
pros: convenient; pretty packaging; may appeal to folks who hate most liquid/cream sunscreens because those break them out.
cons: brush bristles are cheap and scratchy; bristles shed (UGH); price is RIDICULOUS; algae extract may break them out.
I think this broke me out because it contains algae extract. I have used Brush On Block SPF30 with no problems, but when I used Colorescience Sunforgettable SPF50 in Medium for 2 days, I ended up with large cystic acne -- one on my cheek and one on my nose -- at the end of the first day, which calmed down overnight, and then got bad again after using this the next day. I rarely break out anymore; although I have had breakout-prone skin for most of my life, I only rarely get a hormonal breakout on my chin now. I think that the tretinoin I have been using for over a year is really working.
I know the whole "comedogenic ingredients list" is dismissed by some dermatologists, but Lithothamnion Calcareum Extract is an algae extract that is used in cosmetics as a binder, meaning it makes things stick together. Acne is caused by dead skin cells in our pores, and when these dead skin cells stick to each other instead of sloughing off, bacteria feed on these dead skin cells and grow.
Anyway, when I checked the ingredients list before purchasing, I didn't see this ingredient or algae extract; HOWEVER, it is on the box of the Sunforgettable SPF50 in Medium that I purchased and have in front of me. It is the 3rd highest in the list of 15 inactive ingredients, meaning there is relatively a lot of this ingredient in the product. (Active ingredients are Zinc and Titanium Dioxide.) I guess I'm going to have to return this.
Update 9/27/18: I wanted to add that since posting my review above I have been noticing that this product has been sent as free PR and in SPONSORED videos to a lot of social media folks, like youtubers with a very high subscriber counts. And supposedly companies pay an average of $60,000 for a sponsored video -- WOW. Clearly the company has a powerhouse marketing department, getting the product into thousands of dermatologists' offices throughout the country as well as paying youtubers to produce advertorials on social media. I think the high AF price of this product is to pay for the company's marketing & sales staff and activities. I did end up returning this, by the way, since the breakouts were deal breakers. And I didn't break out again after I stopped using it.