I am a Mac user, however I have dabbled with Vista over the last year and have had extensive experience with XP since its release in 2001. Although I prefer Leopard, I must admit that Vista is pretty slick. I fail to see what the complaints are all about. Its a more secure OS and they made it a lot more usable than it was before, with features like Desktop Search.
So why all the fuss? There are complaints that old hardware doesn't work. Since when is it an OS manufacturer's responsibility to make sure every piece of hardware on the planet works on your OS? The OS' API was out a year before it was released. So why didn't the manufacturer of the hardware not make a Vista driver? I think the blame should go to them not Microsoft.
Another complaint is the fact that not all software works. Software compatibility is a privilege not a right! Steve Jobs taught us that when he went from OS9 to OSX. Software developers have been given guidelines on how to program correctly for the new multi-user versions of Windows since Windows 2000! How is it Microsoft's fault when software developers make half-assed software that doesn't follow the OS's guidelines? Actually, the only blame I could put on Microsoft is that they didn't force software developers to follow their OS's guidelines sooner.
The most ridiculous complaint is the one about UAC (User Access Control). Microsoft finally put in place a mechanism to force users to run as limited users. Only when software requires system access will it request access from an administrative user. What is wrong with that? Mac OSX has had that for a very long time! You can't install anything that requires system access without OSX asking you for an administrative username and password. The complaint? "I can't do anything without UAC always popping up." Ahh! The problem once again is related to the latter issue about half-assed software that tries to access system resources instead of following Windows software development guidelines.
That is my two cents.