I recently upgraded to Vista From Xp Pro and i have to say im impressed.
It's actually quicker than XP (Even after a fresh install of XP,Vista is still faster) was on my computer.I Think it supports Quad Core CPU's better?
As far as program compatiblillity goes,i have installed most of games and most of them run fine,even better than XP did - Also DX10 is a bonus!
All in all,i know dont know why people are complaining! Sure it ISNT what microsoft said it would be,but it's better than XP.