received my mba on monday, but haven't really had the chance to spend some QT with it till yesterday. so far after 12 hours of cumulative usage:
the backlit keyboard feature needs help. i'm certain it's a driver issue, and it appears it's a problem with the mbp's as well. i argue that if it's advertised, it had better work. i mean if bmw advertises rotating headlamps, it's expected that when you turn right they also turn right; similarly, the ambient light sensor shouldn't shut the backlight off when it senses total darkness. and yes, sometimes my settings stick, but there's no consistency.
spotty 802.11n WPA performance. for reference, i have a DIR-655 with the latest firmware. anyway, i could be seated right next to the router and the connection will drop. also, streaming video from another computer that is hooked up via ethernet results in choppy playback. i've had to pre-buffer the stream to alleviate the problem, something i haven't normally had to do. interestingly, 802.11g WEP performance at work is fine.
those are pretty much the two biggest gotchas at the moment. but rather than sound negative, here are some plusses:
i now use other features of leopard that i normally don't use. my finder is set to coverflow, and i now use spaces to manage different environments -- it also makes for an effective "boss key" to hide what you're really doing (e.g., posting on the macrumors forum!). i don't intend on adapting those habits to my mac pro however!
the screen is just gorgeous. no dead or stuck pixels, and this is the first machine that i've not had to calibrate out of the box. maybe down the road, though. brightness is close to crt, thanks to the led backlit display.
8-hour charge from 20-100% once. and that was monday evening when i took it home to break it in for a bit. a typical charge is about 3 hours on sleep, on par with gizmodo's observations.
it only gets warm. finally, a machine that puts the lap back in laptop. after 3 hours of use on my lap, i have not found it uncomfortable.
best of all, it's a mac.
hope you all are enjoying yours as much as i am!