I posted last night regarding which MBP would be the best bang for my buck, and I've come to decide that when it comes time to make the jump, I'm going to shoot for the bottom-line SR. Currently I've got a 2.1GHz iMac G5 with 1.5gb RAM. What sort of speed improvements can I expect making this jump to the MBP? I still have to weigh whether I want to ditch the iMac or not. 