This week I converted my family's main computer from Vista to OS X. (It's a Mac Mini).
We pretty much use it for web surfing, web email, really old DOS children's games, and photo editing. Macs do that pretty well.
I still have a Vista machine that I use for the excellent Windows Media Center -- love the record-by-keyword feature and the free programming guide.
But for day-to-day use we're back to the Mac.