I've never been one to use a MBP (of any size) for my graphic design needs. Yes, in a pinch I do. But 95% of my usage has always been through a larger 20"+ display. And it's not so much just page layout where one might need a larger screen, but even developing logos in Illustrator. Just curious where other designers fall. Do you use your MBP screen as your primary (say 70% or more of the time) display or use an external?