I have had a number of problems.
One of the Windows "updates" disabled the on-board sound. I removed the update and it worked again.
The ink level utility for my printer is not supported under Vista (I checked with Epson and they verified it). I am not going to buy a new printer just so I can run Vista.
Whenever I first boot up or restart, Media Payer starts in the background as a "process" and will not run until I use Task Manager to turn it off as a process then launch it as an application. There is probably a fix or workaround but I should not have to spend time figuring it out.
I have had incompatabilities with Photoshop CS3 and Nikon Capture NX. The primary reason I chose a quad core processor is because I post process a LOT of digital photography. If I have problems with two of my three primary applications, I might as well have my old 8088 and DOS 3 back.
I use a smart card to acces the network at the office with VPN. Vista does not support my reader so I have it hooked up to my XP Pro computer. This reader is mandatory so I have no option. It is irrelevant if Vista supports other readers if I cannot use them.
I use Nero 6 Ultra which does not run under Vista. I have to purchase Nero 7. I am using Nero 6 on the old XP Pro machine.
I like to experiment and overclock. There is no way to overclock my 7600GT as long as I am running Vista. Riva Tuner, Coolbits, etc. do not work with Vista.
My fingers are getting tired but I think you get the idea. Why should I have to put up with this garbage when I have available a fast, stable operating system that is far less resource intensive, and is compatable with a greater range of software and hardware than Vista? When Vista's service packs finally gets it to where XP Pro (32 or 64) is with SP2, I will probably move back to Vista.
You should also notice that virtualy every tier one computer company is again offering XP as an extra cost option, I have not bothered to look at the tier two companies. It is also available again on store shelves, and it is selling. That should tell you something right there.