I have to say I've always been a big fan of Bobbi Brown brushes - I've owned a collection of them, never had to replace any of them in 7 years and in my opinion they're by far the best out there.
I bought the travel size version of the Ultra Fine Eyeliner brush to use with my MAC gel liner. It's ideal for creating a sharp, controlled line with any gel liner on the eyelid whilst getting close to the mirror - I find the longer handled brushes too clumsy for a precise line & can't get a great view of what I'm doing. I coat the bristles in a few swipes of gel liner, pull my eyelid slightly outwards for extra precision and then smoothly apply my preferred line style - very easy to use.
The brush does require cleaning every day, but I'm quite lazy and wipe the dried liner off with a face wipe and clean my brushes properly every few weeks, not the best example of brush care but mine's lasted me several years without problems! It's so easy for me to keep it in my makeup bag and carry with me if I'm ever staying away from home.
The only issue is that like others have mentioned, the lacquer and text on the handle have started to crack and come off! Strange, as none of my other BB brushes have had this problem. Also a lid for the brush would be ideal since it does get messy after application and leaves black liner smudges on my dresser and makeup bag - I don't always have time to clean it thoroughly each morning.
I'd recommend this brush to anyone looking for an easy-to-use, quality brush for use with gel eyeliner to use both at home and on the go. Bobbi Brown counters only seem to stock them with particular limited edition products but they can be picked up cheaply on Ebay for under £10.