The new iMac, built with the unibody technique, comes in two sizes, with 21.5- and 27-inch screens. It's got the same edge-to-edge glass of the MacBook Pro and will have Core 2 Duo and new Core i5/i7 quad-core options. UPDATED
The first thing I noticed when playing with the new iMac was that the screens feel bigger and wider, as they should. Secondly, I noticed the black screen and aluminum smaller "chin". Thirdly, I noticed the wireless keyboard, which was missing the numeric keypad (compared to the wired keyboard) and the Magic Mouse. The computer itself has a few things going on that aren't apparent at a glance.