No problems here with Vista at all!! Migrated to Vista Ultimate about a year or so ago on the meachine I built about 2.5 years ago...no problems at all, and actual performance boosts afterward. Also just bought an HP Laptop with vista Ultimate 64 bit and performance is still great.
In short...I won't miss XP at all...it really feels like Windows 2000 Pro to me since Vista was released...previously I always though XP was a LITTLE bit bubbly than 2000.