At work I could probably get away with 19" and 22" but having that extra 19" comes in handy.
At home I find that I don't do as much multi tasking and having 1 24" is nice maybe I will switch to a 30" someday though.
52" Samsung LN52A650, It's not an overkill, I love not having to put on my reading glasses and to have room to have quite a few full windows open and a PIP of TV All while reclining in an with my keyboard in my lap, Track Ball on the arm and my feet up