I think there's something to be said that the MacBook Air is a product that really doesn't have a place in this world. As it was pointed out, it's thin... and really, that's about it. A lot of money for a thin computer. Never have I ever thought, "Gosh, I love this computer, but it's just too thick." I've thought it was too big, too heavy, but never too thick. I have a 15" PowerBook that I love, but honestly, I think it's just too big for me. I much preferred the size of my 12" iBook simply because it was so much easier to carry around. But both are just thin enough for me.
I think that Apple's problem in this is that people were asking for an ultra-portable MacBook Pro and Apple wanted to deliver, but do it in a different way. So they made this thin, thin computer. But that's not what people wanted. They basically wanted the 12" PowerBook but with an Intel processor. Apple made this same mistake before when everyone was asking for a basic Mac computer without a screen that was a lot less expensive than the Power Mac. What Apple gave us was the Mac Mini. It's a nice idea, but nowhere near what was being asked for.
I think that sales of the MBA are going to be great at first and then taper off fast. Everyone compares it to the Cube in that it has a great form factor, but it just is too expensive for what you get. The difference is that the Cube was fully functional, but just really expensive. The MBA is really expensive, but without the function.
The MacBook Air Is a Horrible, Horrible Product