None on the tech side. Tech is there, the thing is, Apple wants the iMac to be thinner every new model, but they won let a fan or a vent thats not a straight line show on the outer case, so the computer cannot cool a desktop processor. Also, since is too expensive/impossible to upgrade anything but RAM and HDD, users will buy a new iMac when they feel it doesnt gevies them what they want, instead of buying a $200 processor and a $200 gpu.
Also the fact that they want the PSU built in, which i find lame, you could do so much more innovation with that free space, and put a brick next to the wall plug like the mini does, its not like you are going to see the damn thing anyways. All that extra space could be used for proper cooling, which will allow for desktop components to be inside again. Also, it might be possible to get rid of the chin by removing the built in psu.
Of course, i still find weird how the iMac g5 had one of the hottest DESKTOP processors inside yet 4-5 years later apple wont put a smaller, cheaper, more advanced, cooler and power efficient chip inside the damn thing.
