I'd like to know this as well. I was in the exact same position as you last December and nearly bought a 27" iMac with 2GB gfx, 3.4 i7 etc... and was all set to pay for it... then actually thought about the reason I was buying it - for gaming, SO! I sacked off the £1800 and spent £940 on an i7 Windows tower, which works better with the creative suite than the iMac does due to the Mercury Playback Engine with the GTX 570.
Can I ask what work it is that you do? Also you mention you have a PC as well..if this is the case and it can handle all the same things the iMac does with ease, why did you buy it? I can only assume it was easier to take to/from uni or something? I really wanted a Mac but just did the sensible cost effective thing based on what I needed it for, sounds like you should have done the same.
Upside I guess is that you'll be able to sell it for almost the same amount you paid for it, they hold their value really well. Better you make that decision while there is a stack of warranty left.