I use Windows 7, and being a life long user of Windows, I still have my chunky 98, I'm too comfortable to make a change, though I might get a Mac as a laptop next time.
Windows 7. I like how it's set up and how it functions, so it's perfect for me. I don't really pay much attention to operating systems on computers, I just use whatever it has got when I get it.
I've got a 4 year old laptop with Vista on it. I've heard lots of bad things about Vista, but the only thing that I have ever experienced with it is there are some compatibility issues with some things. Other than that, it works fine.