The iPhone air would be cool if it had the same look as the current iPhone but about half the thickness. It's be great if they would take the edge where the chrome is currently, make it brushed aluminum and have one single piece of aluminum wrapped around the back of the phone. It's be an even more streamlined look and would get rid of the scratchable, yet very attractive, chrome.
It'd be just glass to aluminum all the way around.
And I'd buy 10 ACDs if they looked like that, albeit a bit thinner as there's no computer hidden behind the panel like in an iMac.