vista. is.. next generation of windows xp...sort of. basically it's microsofts new operating system. soon once it's been out for a while you'll see more desktops coming with 'vista' instead of 'xp'
Without the much touted (and not released) WinFS file system it is basically just XP with eye candy and new bits and bobs, I have found it to be rather bloated and slowish but being as it is only a beta I would hope the final release is a little more streamlined.
Once the UAP and Welcome Centre are disabled it is more usable.
For those who wish to tweak vista a little have a look at this site TweakVista.com