Windows 8
I'm using Windows for a long time now. Since Windows 95 I upgraded every time when there was a new version, I even used Windows Vista which I really liked because of the new interface and the new functions made available (despite what other said that it was a bad OS). I loved Windows 7 because it was Windows Vista reinvented and much more stable, but now with Windows 8 it's a lot of good stuff going on here. The new Metro interface it's very useful and as a developer you can create apps very easy. Still the bad thing about Windows 8 is that with every update they are removing good stuff, with the next update (I still hope not) they want to get rid of the Metro interface and get back the Start Menu with Metro incorporated, but that's just weird, I hope that they will add a function to let you choose if you want the Start Menu or just the Metro.
Anyway, I recommend Windows 8 over any other Windows. Cheers!:-=