Netflix works fine on the Macbook Air and battery life is satisfactory as well. Watched a 2h10m movie from start to finish in Safari, HD quality (streaming at 400 KB/s), fullscreen, 3/4 brightness, 1/2 sound through external speakers. No stuttering, had a little charge left when said and done. Only other app running was running except for Adium (IM chat).
I have gotten over 3 hours before (watched five hour long TV episodes), but now that I think of it, I had the brightness setting at 2-4 bars (since I usually turn it down when I watch movies at night in a dark room). Sorry I didn’t mean to mislead you in the other thread.
CPU usage from Silverlight usually ranges over 110%, so it does tax your computer quite a bit. The fan did come on towards the end of the movie, when RPM is over 5k you can definately hear it. Otherwise near silence.
Tested on a 1.6/4/128 11″ MBA.