I have been using and testing Windows Vista beta2 builds on my work and home machines for several weeks now. I'm finding it hard to go back and use Windows XP, I really like the Windows Vista UI and particularly the entry points into using desktop search everywhere.
Will your computer be able to run Windows Vista? Check out the new Vista Upgrade Advisor that will check your PC for you.
UPDATE: the Upgrade Advisor link is backup and available for download off the above page