The big problem with Vista is when you upgrade a computer that came with XP. You start to find that a lot of hardware and drivers don't work.
Vista is also a PITA for those of us like me, computer geeks that work in IT. I had to turn off many of the security features (UAC) because they simply prevent me from doing my job efficiently.
And the analyst who wrote the requirement that the default upgrade mechanism for Vista would be to upgrade the computer automatically in the background while you work, and then shut it down automatically needs to spend about an hour in an ultralight in a 50 kt. gale. When the weather is too crappy to fly (I'm a PPL and Beech owner), like it has been most of the winter, I like to fiddle around with MS Flight Sim. Imagine my horror when I had a perfectly set up instrument approach in a DC-8, to minimums, when the damned computer shuts down automatically.
Non-computer geeks, I heartily recommend you get a Mac and save yourselves a ton of grief. With today's Intel-based Macs and Boot Camp you can install Vista (or XP) on a separate partition and run Windows natively (or you can use VM Ware or Parallels or some other virtualization program).
I did that, and I find that other than to run Flight Sim or test a chunk of the software help design, I rarely bother with Vista. Mac rocks!