Desktop: Windows 8.1 Professional x64 (Update 1)
Tablet: Windows 8.1 Professional x64 (Update 1) (Surface 2 Pro)
Mobile: Android 4.4.2 KitKat (Vanilla)
I have a flash drive with Linux (Ubuntu 13.10) on it as well, but it still doesn't offer nearly enough to compel me to switch from Windows. I still like to play around with it though, and it's handy to have just in case things go pearshaped with Windows.