I will amend my comments, it is indeed the manufacturers issues with driver, not MS.
I currently do not run Vista on any of my machines. I have however got about 3 betas and both RC's on disk that I have used along with Ultimate 64 and 32 bit flavors.
Ran Betas and RC1 on my old laptop (P4 2.4Ghtz, 512MB ram) and it installed (after turning the pnboard graphics down to 8meg). Only real issue woth it was the speed. It was slow, put it down to old hardware. Didnt use it for more than about a week, then it broke so got a £500 voucher for it.
Ran Betas, RC2 and Final 32 bit Ultimate on my iDEQ SFF. ITs newer than the Laptop. Nforce 2 mobo, AMD XP2100+, 1GB RAM. It was very confusing. sometimes would load without half the programs, sometimes would load fine, sometimes had an image, sometimes didnt (nVidia drivers fault I admit). Would sleep, then resume, then sleep, then not resume, or simply just not sleep? absolutely no support for my TV card (again, drivers). there was a lot of other niggling problems i cant really remember, just the inconsistency with it. some things wouold work fine, then when you restarted the machine, they would not work. Most of the issues that werent drivers were not present in the beta or RC, but only appeared in the final version?
On my newest machine, my PC (E6400, 2GB RAM, 7800GT) I have run both the 32 and 64 bit versions of RC1, RC2 and Final Ultimtate. By now drovers were up to date, and I didnt have many problems with them. but sleeping was still a nightmare. sometimes sleeps, sometimes doesnt, sometimes resumes, sometimes doesnt, etc. and I lost a lot of performance. was getting 30FPS in CS:S on Vista whereas the same settings in XP were sitting nicely at my vsync capped 70fps, with the occasional drop to 60 odd. Was impossible for me to host a server and play on CS:S on vista, just lagged, not bandwidth of graphics, just a slow machine. So went back to XP, and havent touched Vista in about 2 months.
Basically, yes, Vista has a lot more in it that XP, yes I understand the drivers are the major issue. but I dont want to fiddle this and change that and use this specific driver for this (was choppign and changing about 4 sets of nVidia drivers for my SFF). XP 'just works' 99% of the time, and that just makes it a more logical choice.
I live in a student house with 7 computer in it, and only the brand new Vista machine is the one im called in to help sort out. We all share our files around, and the sharing in Vista is just a little annoying. Installing any games older than a few years is a hit and miss operation, and its just slow. What makes matters worse is that its a PC shop bought PC, so comes bundled with the resource hogging crap that comapanies shove on new machines that you never need! 6 XP machines, no issues, 1 Vista machine, issues almost every day, although half are user error due to everythign being in a different place in Vista than XP.
So, as you can see, ive had quite an extensive use of Vista in both its development and final stages. seen and used developments over 4 years, and used it on 3 personal machines, girlfriends top end Vaio laptop, mates laptop, and housemates PC, and have never experienced a problem free setup. It could just be my luck...