Backstory: I was running Windows Vista Ultimate edition 64-bit on my personal computer for about a year. I eventually went back to XP, as there were some hardware issues with my older system and Vista was generally much slower than I found acceptable.
In my day job (in other words, the time I’m not herding cats) I get to work on many different systems. We’ve been using Vista for a little over a year now, and finally have found a system that makes this latest incarnation of Windows work as it should. Not that the other systems have been slow; 2GHz+ Intel Core 2 Duo processors aren’t exactly slow (they blow away my 2.2GHz Athlon 64 in the Super Pi benchmark) but Vista is so big it just takes a lot of computer horsepower to make it slick; on similar hardware, XP is much more responsive.
The particular systems are from Dell, but they could be from any OEM or basement home-brew. The important parts of this smooth and responsive system are the upgraded Quadro (professional version of the GeForce) video card that makes the Aero UI animations smooth as butter, and the 3.16GHz Core 2 Duo E8500 processor.
Now I’ve been exposed to Vista on a fast system, I find myself re-examining my next system upgrade. It’s not going to be happening for about a year, but I was seriously considering either a Mac Book or the mythical “xMac” should Apple cave to pressure and introduce a system between the Mac Mini and Mac Pro. But now… I can see a fast Core 2 Duo, overclocked with 8GB of memory and 10krpm drives running Vista Ultimate x64 in some kind of smart aluminum case. That wold be one nice system… 
One day.
