@Mike
:) "Vista is fast". Have you been sleep typing again?
I myself have used Microsoft products from DOS to Vista (missing ME out) & built a system using top-notch hardware (with 2GB RAM) specifically for Vista. It runs... well... adequately, but on more than 1 occassion I've been tempted to go back to XP Pro which I know would run at a blistering speed & improve my productivity tenfold.
Therefore, I've got to disagree with your vendors statement. From my point of view they're not the problem... Microsoft are clearly at fault in my eyes. And how many years did they spend developing this product?
Vista's a touch on the lardy side for my liking... really can't understand why it needs to be so bloaty either. Even Microsoft seem to be struggling to comprehend their own code judging from the update fiascos we've had over this past year.