I currently have a 17inch c2d 2.8, I am thinking about adding a 15 inch i7. I don't need a second laptop but will get one in the next year. One for work and one at home. I was waiting for a redesign. My question is, is the i7 just a speed bump or a game changer? I want to put some difference between the 2 machines, so they don't come up for upgrade at the same time. I wold consider the switch to unibody/sealed battery a design game changer. How about the i5/i7