Engadget has posted a hand-ons of the new iMac released earlier this week. Engadget also offers a gallery of the iMac unboxing. Externally the iMac has changed very little, the FireWire 400 port has been removed and replaced with an additional USB port and the Mini-DVI port has been replaced with a Mini DisplayPort connector.
iFixIt has also posted a gallery, but this time of the disassembly of the iMac. As with the external of the iMac, the internals are largely unchanged, of note Apple has kept with CCFL backlighting rather than switching to "greener" LED backlighting.