I use my Powerbook (15", rev before the last PPC revision) in class, and need it for a good 4 hours or so during the day. To acheive that, I turn my brightness way down as to not drain the battery. Usually by the time I get done with my last class, I'm down to 10-15% charge. Problem is, I can hardly see the screen. How much of an effect does brightness have on battery power? If I turn up the brightness, will it use a significant more amount of power? I do turn of Bluetooth to save battery, but turning off Airport isn't an option....need something to do during those boring lectures Thanks. And on an unrelated note, someone sitting near me just pulled out his Alienware laptop....that thing is about as thick as 2 of my PowerBooks put together! Probably cost him the same as 2 PowerBooks too.