Joanna/Olivia - sorry about the geek talk. :D In summary, it's an interesting computer but I think that for most people, its compromises might outweight its usefulness.

Pam - good points. To upgrade software including OS upgrades, the easiest solution is probably buying the external Superdrive. If that's not an option, then Apple has a crazy idea about using other computers on your network (whether Mac or PC) to upgrade your Macbook Air (this is a really strange idea)

http://www.engadget.com/2008/01/15/apple-announces-remote-disc-to-wirelessly-install-software/

And as to the non user replaceable battery, it turns out the cost of the battery is the same cost at the Macbook Pro's battery and installation will be free. You're still out the time though that Apple will need to have the machine to do the battery swap.

Frank - the weight is correct. There's really no way to get the weight down further significantly and be able to maintain the full sized keyboard or avoid reducing the size of the LCD screen (the screen on the Macbook Air (13.3 inches) is bigger than your D420 (12.1 inches)).

Still I agree with all of you. I think that for most people, the regular MacBook is probably a better choice - more flexible without odd restrictions though it is heavier (5 lbs).

Masaki