I ran into these today at Sephora, and I really like them. The consistency reminds me of MAC's studio fix concealer; and it also reminded me of Sheer Matte. I like to take a drop of Sheer Matte, let it dry down a bit and then apply it.
A few swipes on the finger tips is enough to cover under my eyes. I was in a hurry, so I didn't have time to really match my color. I just picked a brown and went for it. It might have been Cafe. If I have time to play another day I will. My only concern is the price point for the amount you get. Its a straight up splurge. Other, cheaper concealers work just as well. What I do look for is something more yellow tone. I think the NARS colors offer that. I am going to investigate more.