Vista seemed to be faster than Xp to me.
Did a test of Vista XP on a new laptop (imaged the drive that had Vista Basic on it so I could restore it later, and Vista Basic *definitely* ran faster than XP and handled memory usage better...with the caveat that I did have 1 GB of RAM.
Quite happy with Vista Basic since it came with the computer. Might be less so if I was paying for an upgrade. Just like after XP's release, you do need to be wary of driver issues for awhile (or wait).