I've been running vista for a few months, no major problems. Well, none I couldn't fix

I have the luxury of an XP pc sitting right next to it incase I need it. But overall, if your getting a new PC with it all installed and the right drivers, that will eradicate a lot of the problems.
Do you want to pay for XP now and then pay for Vista again when you decide you want it?
There are some nice features on vista. The main ones I have found and like are the speech recognition, much improved task mananger and the side bar (lots of gadgets to download for it). There are of course lots of visual tweaks, windows aero, 3D-alt tab as its been put, although it's actually windows+tab, alt tabe gives you previews of all open windows in a box. When you mouse over any taskbar windows you get a preview, useful if you have lots of browsers open and you don't know which is which. And coupled with Office 2007 everything looks nice indeed.
There are more useful features, and some that are a pain (like finding my way around the network settings

), I turned off User Account Control as 90% of people will.
You could alwyas dual boot your PC with vista and XP.
http://lifehacker.com/software/top/windows-vista-beta--how-to-dualboot-windows-xp-and-windows-vista-179906.php