OP, 4 sounds right based on what you're doing. I always say take 60% of the claimed battery life for real world use.
For the weight, the air is still top in class. For the run time per watt hour, still top of the class. For longevity of the battery, still top of the class (never verified). I don't understand how come more people don't trump this aspect of the air up--battery lasts 3 times longer (1000 charges) compared to other batteries. All other laptop batteries that I have had are down to like 65% after one year. So to me it's the sustained battery life over time (the first 2 to 3 years) that should matter most to people. In that respect, your air will still be getting 4 hours for alot longer than other laptops, who may eek out ahead brand new, but will lag behind in not too long.
Never understood why Flash is so terrible. Maybe it is. It seems like as soon as jobs said flash stinks, everyone decided that it does indeed stink. It does cause an inordinate number of crashes, but maybe that's b/c it's powering an inordinately large number of programs these days.
