Vista:
- Slow
- High requirements, offers nothing worth it
- The main advantage, Aero interface, was already in use on other PCs and can be used in XP
- Doesn't work with older machines, too old procs' and graphics
- A lot of existing ones don't work, cause there are no good drivers
- DOS things and epic games work worse than on XP
- The longer it works, the slower it gets
- Some xp games dont work too...
- Good programs don't have licenses under vista.
And that's it. Oh and that Vista's support ends in 2012, XP's in 2014. And Windows 7 comes out not-so-long-from-here. Vista is like a beta version of W7...
Everything and more here:
http://en.wikipedia.org/wiki/Criticism_of_Windows_Vista