What's POSIX?RAKtheUndead said:Linux, most definitely. Today's Real Computer Users really should have some sort of POSIX compliance, and that isn't something you get in any Windows version.
As for me, while I would have to go for OS X for looks and efficiency, my winner would be Windows XP. It runs well, fast and I've had years of experience with it; even if I'm not getting the most out of my RAM, XP is just so much more efficient than Vista.
However, Windows 7 is looking pretty. It may be something I will take a look at when it comes out.