I'm hopeful I didn't misread the slide, and that the original Macbook Air will be supported. Not my primary laptop, but it'd be great to move up from Lion.
Maybe because the App Store requirements, rather strangely, say "OSX 10.6.8". I suspect that might well be why it's free - can't have lots of people paying for something they can't use, much easier to do the checks during installation than at POS, and there will be a LOT of compatibility issues with various machines on the cusp.
I tried buying Mountain Lion on a machine that ran Lion but doesn't support ML, and the App Store does have hardware checks at point of sale. It won't let you buy/download it if your machine is incompatible.
