The hands-free aspect of using a bluetooth headset with your phone is definitely a plus, but actually wearing one can be kind of a drag. Personally, I always feel like an idiot/jerk wearing one, especially in public.
I'll wear mine from time to time if I know I'm going to have to be on an overly-long call with someone, and I know I'm going to need both hands and a full range of motion, but usually I avoid them. Headphones with a mic in them are my dream solution to phone-holding problems, but I usually just hold the phone up to my ear like a chump. How about you? You wear one all the time? Never? As a fashion statement? Only on Thursdays?