I feel your pain. I purchased a Powerbook G4 2 weeks before the Macbook Pros came out.
But...
Part of being a 'smart' shopper is to look @ the product life cycles. It's been speculated for some time now that Apple will revise the IMac @ MWSF. The timeline is also pointed out in the Buyer's Guide.
I wanted to buy the new Imac back in August, but I saw the guide. Then later on I saw the vid card problems, and since I didn't 'need' it, I decided to wait until Jan.
I wouldn't worry about it too much, especially if they are minor speedbump improvements. If you need it, then buy it....Computers are updated anywhere between every 4-6 months, so why beat yourself up over it?
🙂