I've had some niggles here and there with my install of Vista64, a few locks, a few crashes with certain applications but to be fair, I had similar issues with my previous XP system as well.
I wouldn't advocate anyone upgrades to Vista, but at the same time I wouldn't advise anyone to avoid getting a new system specifically because it comes with Vista. There's nothing majorly wrong with it, there's no glaring errors or omissions I've come across and the new interface (once you get used to it) does make things easier (though possibly due to the fact it's similar to the Windows 2003 systems I've been learning)