From what I understand, a big part of the appeal of the MBA is that it's light and thin enough that you can basically forget that you've got it in your bag. For people who travel a lot, that's a big deal. For some users, then, the laptop's physical attributes (dimensions, etc.) are important aspects of the machine's overall usability.
you can basically forget that you've got it in your bag
Except you can't, because you're worried about crushing it, due to a relatively frail case, or you're worried about scratching it because it looks pretty.
This is why I ditched an MBA and carry around a netbook.
