Suspicion has been growing strong that the new Macbook has less battery power compared to the old one. About 16 percent less to be specific. The old battery was rated at 5600mAh/60Wh, but the new ones are rated at 4700mAh/50Wh. This perfectly explains why you now need to use the integrated Nvidia GeForce 9400M on the new Pro to get the same five-hour (rated, not real world) battery life as you did with the discrete 8600M GT on the previous-gen Pro, despite its use of more energy-efficient DDR3 memory (which would negate drops from the faster FSB) and the same processor clock speeds.