After using my first MBP for a while, I'm kind of regretting getting the 15 inch. With the high-res screen, and as long as you have good eyes, the 13 seems just as functional and more portable. I love using my girlfriend's. My two cents, if Nemesis ends up going with a MBP.
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.
Note that the Airs have much more manageable screen real-estate than the 13" MBP: the 11" already has a higher resolution than the 13" MBP, and the 13" MBA has the same resolution as a non-HD 15" MBP.
I love my 13" MBP. It drives a large monitor when I need it to, and the rest of the time it's very portable and comfortable. I forget the screen is small, honestly.
