I am going to be getting a new mac soon and I know it will be a powerbook. The 17in is out of my price range but I can get the 15in if I wait for a couple more weeks, or I can get the 12in now. Does the 15in combo drive offer enough more screenspace and ram options to make it worth-while to get instead of the 12in? I think eventually I would like to have it at 1gb of ram. Also, can the 15in combo have a backlit keyboard, and is it still easily portable?