I have had Win 7 installed under Bootcamp on my 2011 27" iMac for some time now. I was always a little worried that the computer got very hot when in Windows because the fans don't operate properly when not running the Mac OS. Well, recently MacUpdate had a software bundle they were offering for $49 that included a lot of great programs, like Screen Flow and Parallels (plus about 9 others) all for $49. I took the bait and installed Parallels using my Boot Camp install as the Win 7 source. I can still boot natively under boot camp, but now I can also just run Win 7 simultaneous with the Mac OS. What I like about this is that, as long as the Mac OS is running - even if I'm on the Windows side, the fans operate properly and my iMac stays cool! That alone is a big plus for Parallels over just using Boot Camp alone.