Re: New 27" iMac
...in all seriousness - the only thing I can say about the 24" & 27" iMac is the screen is far, far better than the smaller ones. The smaller iMacs use a low-quality screen in comparison, they only have 6-bit color depth and the viewing angle suffers because of the nature of the design (on-par with the $150 PC monitors you can get at WalMart). The original 20" iMac came with a high quality screen then Apple updated it with the cheap Walmart version.
The 24" one has a wide-gamut screen with 8-bit color depth. Due to the nature of the panel they use, the viewing angle is much improved - meaning you can shift your head left, right, up, or down, and the colors/contrast doesn't shift much.
The bit-depth thing doesn't sound like much, but when viewing something like a blue sky that has a slight variation in tone from one side to the other, the 6-bit screen may show dithering and "blockiness" while the 8-bit screen will be much purer. The better screen is almost necessary (IMHO) on larger panels because of the viewing-angle issue, but if you're not doing photo work I doubt you'd notice the color-depth differences.