Yea, I tend to agree with the OP that the MBA battery has still got quite a fair bit of room for further improvement
I'm like Scott who type a lot, and I put brightness on 1 block, just enough to see what's going on the screen and quick typo checks
with BT & WiFi off, I managed to squeeze 4hrs of battery life
I have been in scenarios where I have to let the ambient light sensor to tune up the brightness and the battery only lasted ~3hrs
it's very disappointing, i agree
this is also the reason I am very committed to all means to extend the battery life (i.e. fan rpm control, thermal paste, brightness...etc)
The battery does not last long enough when I am working 'full-on',
still it's still capable in most of the other, normal-use situations