I love, love, love Studio Sculpt concealer and unfortunately the rumors of it being discontinued, are true. I do love Studio Finish concealer too, so at least there is still another MAC concealer available, for me. I still want to keep purchasing this one too though! I'm still going to tell you what I think, because it is bound to still be available in stores. (wishful thinking?) So firstly, I think it is the thickest, fullest coverage concealer I have ever owned and blends very well as it is super creamy. Of course MAC has a huge shade range in all their foundations and concealers, so there'll be a shade for you.
I currently have mine in NC20 and change my shades to what time of the year it is and how tanned I am. As you can see from the swatch it is very covering and works for me under the eyes, over redness and to cover blemishes. I blend mine in with either my finger or my MAC 224 brush. I wear Studio Sculpt with MAC's Studio Fix Fluid foundation.
Have you a favourite concealer?