I've heard it's about 5 hours with light usage (assuming everything is turned off and brightness is down to about 3 bars) but have also heard people complaining that they're only getting around 3 hours? To be honest I cant see myself paying £749 (with student discount) for something that's meant to be for portability but runs out that quick. I already have a 21" iMac so I have no need for the 13" and would like the 11" for portability (or if the 13" mbp could run sims 3 properly then I would sell the iMac and get that.. but that's another story). Also is it hard to read the screen? I use a friends iPad2 during lectures to read separate powerpoint slides just fine and I believe that's about 2" smaller than the air?