I completely agree with you, Apple seems to be getting rather OCD about shaving off another 0.Xmm just for the sake of it, which is completely unnecessary on a desktop. When was the last time you heard anyone say "I wish my iMac was thinner"...?
It's pretty ridiculous too that they have to use an expensive and slower mobile CPU and GPU just so they can save a few millimetres... I'm pretty sure they wouldn't loose any sales by having perhaps an internal PCI slot with the GPU in, which would have fitted in the older aluminium design no problem. How about user-upgradable RAM too? What happened to that?
Yes, I'd have been happy with a faster version of the previous iMac.
The thickness is completely irrelevant to me and an optical drive would
still be useful. I've ordered a Mini and an external optical drive instead (so Apple
have lost some income) and am keeping my 2011 imac to soldier on at work for the foreseeable future.