I use Windows 7 and Linux Mint. Most of the software I need for work and university is Windows only, some of it does work with WINE, but I just find it's easier to use it under Windows. I keep Linux around because I like learning about it and getting my hands dirty (I use Mint specifically at the moment because I wanted to try it to see if I could survive on one of these "desktop friendly" distros as my main OS - before that I had a Debian partition). Most of the programming I do is done under Linux, rather than on Windows (aside from Visual Basic, obviously). I find it's easier to just bring up Linux on my laptop to knock up a quick Perl script rather than try and battle with Cygwin on Windows.