The Touch Up brush from Bobbi Brown is a serious multitasker. This brush earns its keep in a big way, doing just about anything I require from it. Basically, this is a fluffy blending brush made of natural hair. It's good for both cream and powder products- eye shadow, concealer, foundation and even contour/highlighter if you're up to it, though it's on the small side, so it's more for around the nose than the hollows of your cheeks.
Despite the different shape and size, the most comparable brush to Bobbi Brown's Touch Up is the classic MAC 217. I use them for the same purpose: blending cream products and doing clean-ups and touch ups all over the face. The Bobbi Brown is more densely packed and softer than MAC 217, and holds its shape significantly better (seriously, it seems that the quality of MAC 217 brushes has gone downhill in the last 5 years. My oldest one looks and feels nicer than the one I bought last year). I use it less for powder shadows, simply because I have other brushes I prefer, but it does the work. The touch ups also include setting small areas with translucent powder, evening out if I'm using more than one concealer (it happens).
Bottom Line: a not-so-old reliable.
Bobbi Brown Touch Up Brush ($28) is available at the counters and bobbibrowncosmetics.com.
All photos are mine.