I have a 2011 27'' imac paperwait on my desk (bad GPU, flaky power supply). I would be very careful if I were you. Personnaly I like windows 7 better, I just get things done faster because I do not know the Mac shortcuts.
Also I have issues going on/off VPN with OS/X, whereas it was pretty automatic on Windows. Where the MAC shines (when it works) is recognizing USB devices and the build-in apps (photo and garageband).
Next time, I will buy a $500 Dell and a $2000 Gibson, 20 years later you can still enjoy it. Good luck.
I have 5-27" 2011 iMacs here at the office and never had a problem with any of them. Have you tried taking it in for warranty work? Then you wouldn't have to spend $500 on a dell and you can still buy that Gibson!