While in the strictest sense, this is not a concealer, it can boost the abilities of any true concealer (and, of course, Bobbi recommends using her own Creamy Concealer over this) for correcting discoloration. The only place I use this product is under my eyes. If I stay up too late, or don't use an eye cream, or don't sleep well, I have purpley-blue circles under my eyes. When I bought this, I was using MAC's Select Moisturecover concealer (shade NC15) to try to cover up these circles, and it wasn't working (I purchased this concealer on the advisement of an excellent MAC sales person at my local Nordstrom). When Bobbi Brown had a Friends and Family sale, I jumped online and picked up her corrector in Porcelain Bisque, the lightest shade available, without really know if the color would be right for me.
For $22.00, you get 0.05 oz of very creamy, fairly thick-feeling (really, very close to a paste-like consistency) corrector. The pot has a itty-bitty mirror in the lid, and is about the same diameter as a MAC eyeshadow. I was extremely unimpressed by the amount of product when I first opened the box. It's extremely pigmented, though, and you don't need to use much. I believe I've had this pot for over 2 years now, and yet, I haven't finished it.
I usually apply this with my MAC 242 brush, and then buff with my MAC 224 (which makes an awesome application brush for liquid concealers!). On it's own, it's not flesh-toned on me at all. It looks almost white under my eyes, and while I am on the fair side of skin tones, I'm not that pale. I'd wager fairer skin tones could use this as a concealer, if they wished.
If, however, you are using a light-coverage concealer, or have discoloration on your skin that your foundation cannot manage, I'd recommend this product.