I sold my older 15in MBP to get a unibody 13MBP. I lasted 4 months before selling the 13 to go back to 15in (thank goodness for high resell values.) The little bit of extra space just makes it so much easier to juggle open windows and see data from different programs while working. People think I'm a major multitasker with they see all my open windows, but really I'm working on one task with lots of varied inputs. I'm a little worried that Lion might take this away from me, with its emphasis on single window apps.