I think Windows is a great OS, but in many ways, I love Linux even more. In fact I would very likely migrate over to Linux if it supported all of my Steam games...
...which is a problem. It's a big problem. If I move to Linux, 90% of my Steam library will become unusable. Yes, I know Valve is making big strides to support Linux, and more and more developers are jumping on the Linux bandwagon, but that doesn't change the fact that literally ~700 of the titles already in my library are going to be utterly non-functional in an OS they weren't made for.
Right now, in Windows 8, I can safely say that pretty much all of my games work flawlessly out of the box. It's not something I'm even concerned about. Even a lot of the old stuff, like XCOM, Fallout, Gothic, etc, etc, all work with no tweaking required. Which is the way it should be, no?
If I move over to Linux, then I will be abandoning that. This has got to be the biggest elephant in the room. Some newer games will be patched to include Linux versions, yes; and Valve can certainly put pressure on devs to start building Linux games; however, there is absolutely nothing Valve can do to convince an old studio (possibly one that doesn't even exist anymore) to go back to a game from 2003 and re-tool it to run in Linux. It's just not realistic at all.
And no, I shouldn't have to deal with the headaches of running WINE. If I want to play a game in my library, I want to be able to press "Play" and leave it at that. Not worry about Linux support.