My one major pet peeve with the MacBook Air is that no matter what I do, it seems that this machine never goes fully to sleep. Somehow the battery is being drained (albeit at a slower rate) when I set the computer to "sleep" or when I close the lid.
This has become an incredible annoyance as my main purpose for this laptop was to be able to use it on the fly. Lately I've found that I have run the whole battery out in about 8 hours with less than one hour of actual usage. At first I thought it was because the Airport was constantly scanning, which often drained my old MacBook Pro.
My two theories are that if you bump the machine it somehow triggers the hard drive to spin up or that there is a software glitch that needs to get fixed.