When I first saw this thread I was tempted to say "don't" simply because of my experiences with what the Air Force is doing with VISTA and how they are going about it. If you are in an environment where you don't control or at least have a hand in testing what apps you use, it's absolutely not worth it.
That said, I've changed jobs now and do mostly database administration using a combination of Red Hat Enterprise Linux and XP 64 Bit.