Why only those three? They all belong to Microsoft so, the "Who" is irrelevant. I personally use Debian Linux and have been for many years. I simply utilize it because I can make it work for me, versus me altering it enough so I can work in it.
I've also utilized Windows XP, Windows 7, and Windows 8 through relatives and work, and I don't have any complaints with any of them, really. They work, they function, and they really aren't that difficult to use.
Then there are Macs, which I haven't used since college (sorry Mac lovers). I again, don't have any real beef with them, other than they've desperately been trying to lock down their platform (including where you still apps from). I see advantages and disadvantages to that, but I'm not sure I like it (Microsoft is attempting the same fate with Windows 8).