Extra cost for the 5400RPM drive on the 15" 1.25Ghz powerbook is like $120 give or take.... Is it worth it? what kind of performance difference is it between the 5400 and the 4200 rpm drives? (both hitachi I am asuming) What about heat and battery life? Is the 5400rpm drive hotter and more power consumptuous? I placed my order for the 5400 rpm drive in a 15" 1.25ghz/superdrive, but am having second thoughts.. I think I'd rather have longer battery life and cooler operation than unnoticable performace gains... but just how much performance comes from the faster spinning disks?