You're generalizing. The drivers for Vista are much more mature than they were a year ago. Sure, they got more maturing to do. And with Vista SP1 coming out soon there will be more improvements. XP had its share of issues with drivers well past a year of release. XP wasn't really solid until SP1 came out and got even better after SP2.
I bought XP the day of release and I bought Vista on the day of release. XP was far less problematic. Vista even had issues with my MX518 USB mouse being connected to a PS2 adapter on a PS2 KVM. XP had no such issues with that setup at all, nor Linux, nor WinME. I had to go spend over fifty bucks for a new USB KVM thanks to Vista.