One of the most hyped concealers back when it came out was the Too Faced Born This Way Concealer (available at Sephora, here), for $28. One of the things that I'm always concerned about is oxidation. 

If you're not familiar, many base products like foundation or concealer, darken or change color when they dry exposed to air. When you're testing for a good shade match, it's a real bummer when you've bought a concealer you love, and then it turns bright orange five minutes later.

To help you get some idea of this, I got my hands on three different shades of the Too Faced Born This Way Concealer, and photographed it 15 minutes apart, so that oyu can see the effects of oxidation. If you're taking a look at this particular concealer, I would definitely wear it for a few minutes before buying.

As you can see, espeically with the lightest shades, there is a significant color change. Is this a great concealer? Aboslutely. It wears evenly, without creasing, and looks so natural. Definitely try to find your perfect shade match.