I would love a 50 f2 IS.
I do like primes, but I have also realized I really don't need anything faster than f2. IDK if it is the subjects I shoot vs distance or what but I use f2 on my 50 and f2 on my 135 (I guess I need the 200 f2 as well). But alas, no bueno on the 50 f2 IS from Canon. I'm going to try the Tamron primes and see if I can get one with good AF.