Gizmodo provides a gallery of screenshots and video documenting the disassembly of the MacBook Air and shows that it is relatively easy to access the battery, which is held in by a number of screws.
Aside from the innards being well designed, the disassembly of the MacBook Air was surprisingly easy. Hands-down the easiest Apple notebook we have ever taken apart. There'* basically only one step to get inside the machine, just unscrew the bottom casing.
Semi-waterproof keyboard, semi-waterproof screen. 1.66GHz, 80GB 7200RPM, 2GB Ram, 500 nit brightness screen (twice of Apple), and of course fingerprint security (slide finger in order to login to windows).
and I can drop it on a concrete floor and not damage it.
did I mention I payed less than half of what the Macbook goes for?