The primary issues with Windows Shitsta is that it's a resource hog and desktop navigation that used to take a click or two now takes 3, 4, 5 or more clicks (Windows Task Manager, anyone?).
Those extra clicks add up over the course of a day, and amount to thousands of extra clicks each month (or week, in some cases).
The fact that there are software compatibility issues is just icing on the cake.
The only computer I've bought in 2008 is a Mac (still in the box 2 months later! lol), but last year, I bought 2 PCs and a laptop and all had to be upgraded from Vista to XP after I got them home and found them unbearable to work with.
The people who 'like' Vista are just stupid people who don't realize what computers are here for.