What Operating System do you use?

I'm using Mavericks for school and work. Win7 for gaming.

well i used windows7 , but planned to change to windows8 in the future since my mobile phone is also a windows8 phone to :D
Windows ROCKS!!

win 7

Windows 7

Win7 and happy with it

I mostly use Windows 7 (Home and Ultimate) but have also tinkered with Linux (Ubuntu/Kubuntu/Mint).

bleeding edge.... ARCH LINUX...

I also use Windows7 , windows 8 still has many bug !!

Windows 7

Windows Xp