What do you run? I've got a hacked copy of Windows XP. It's run its course though; not only this copy but XP in general, and possibly Windows as a whole. When I get off my ass and finish my backup drive I'm switching over to Ubuntu. I've used it and it seems to be a lot less of a resource hog and can be nicely stripped down to the essentials if that's what you need. I've seen it in simple forms to massively tricked out, so the versatility is pretty impressive. The only thing I worry about is having to manually work around some things to get my Windows compatible software to run in Ubuntu. Although I have to admit I like the fact that it will probably discourage me from installing extra crap because I'll only feel like doing it for the essentials. Best of all it's free, so no more having to pirate or work around things. And I imagine it being somewhat less prone to infections and things of that nature.
Oh shit first post from Ubuntu. It's pretty- uh, well I'm gonna have to work some things out then I'll judge.
As a fervent Microsoft hater, I really don't like saying this but... Windows 7 Ultimate is pretty solid.
Eh, it's a waste of money for Ultimate compared to Premium, though. There are (counting on fingers)... 8 computers of some form that are used in my house. Operating system tally: Vista: I Windows 7: II Windows XP: II OS X: III