Personally, I would just stick with vista because:
1. Even if it is horrible like people say, the service pack is still coming out next month.
2. Even if it is horrible, direct X10 is rolling out very soon so if you want to play the newest games, you're going to want vista.
3. Xp is officially discontinued by the end of this year (or sooner) so that means you have to spend extra money to buy vista when you could have received it with your new PC.
4. I ran vista for 4 months now and honestly, I have never ran into any problems yet. I've also found that since vista comes on a new laptop and because we are still unfamiliar with 'new' things, we blame vista for everything. When the computer crashes, "oh its vista, vista sucks!". When my mouse wasn't working, "oh, its vista, man vista is so crappy". I didn't realize I was doing this at one point too, but yeah......I think we all did.
5. Like someone else said, keep vista and install XP for now right? Vista is going to be around for another 5 - 10 years so at least you won't have to buy it again.