I'll say in my first three months of having Seven I was virtually doing a weekly re-install/repair. And that was down to me, I was trying to use it like I used XP and it didn't like what I was doing (I customise, heavy. Is there a Computer Customisers Anonymous?). But once I realised I needed to "forget" XP and move on I've done one repair install, and that was a choice matter.
I visit my daughter as often as possible (200 miles away) and every time I arrive I'm given her Vista Lappy to sort out. In comparison, after user error

problems removed (ME!!), Win 7 is very stable. I'm glad I hung out for it, that's for sure.