While I would definitely agree with you about OS X > Windows... I won't agree that the current iMacs are "very nice". They are severely underpowered compared to what is available right now, let alone at the price they're asking.
I use a PC at work for heavy CS6. It's an HP tower running W7 and it freezes, crashes etc. To be honest, my 2011 iMac running CS5 does not have any of those problems, and believe me, I'm working with large files. Also any CS App opens in half the time on my Mac. Just saying.
(Work PC is quad core i7 12Gb Ram) Mac specs below.