Just wanted to chime in. I am doing the opposite of the OP. Figured I'd share my story for the heck of it.
I am recently selling all of my computer components on eBay in preparation for a 2012 iMac. I had a nice gaming rig, but it turned out I only played Blizzard Games, or indie games off Steam that weren't graphically demanding.
For me, I am switching back to Mac. I have been a huge Mac fan since 2001 and have been on board from 2001 to 2009 when I got bit by the "pc building" bug (thanks to Wow and it running better in Boot Camp - guess it opened my eyes to the PC gaming world).
I switched and sold my 24" 8800gs iMac (just as well, reading all these defect stories make me cringe and wonder what happened to my former iMac).
Then after tooling around with Windows 7 and typical PC hardware for a year. I switched back to a 27" iMac mid 2010. I plopped an SSD inside, and it was great. But I missed the raw power of a PC. So I switched back - AGAIN. And now, a year later, upgrading hardware on and off, I am switching back once again. This time permanently - or else my wife will kill me.
I miss OSX and the elegant simplicity of the iMac. I know I will miss upgradablility on a PC and gaming in Windows (even Bliz games get an advantage with Windows in situations where hardware is equal and the OS is the determining factor). I guess for me, I am getting to the point in my life where work and family are cutting into my PC gaming time and tinkering time. I'd rather just have something that is limited in a sense, so I don't waste any more time and money on upgrades.
My wife still has her little ITX AMD A8-3870k "gaming" PC, that should be enough to tinker with for now. Until I turn her over to the 2012 Mini... lol.
So in my experience, I've switched a few times. However, my heart was always with OS X and Apple.