Well all other manufacturers have much wider line ups. And some offer quite some innovation when it comes to body structure. Magnesium/titanium sceletons, carbon fiber bodies, liquid drain holes, matte screens, higher resolutions, more ports... OSX and style really are the only appeals of Mac Laptops. At least to me. If apple sold OSX as standalone and there were drivers and support I would have a hard time chosing between a MBP and a t400.
I know the feeling. I have all bur switched completely and use my X200s (magnesium frame, carbon lid, drip holes, 54mm expresscard-slot, SDHC-card reader, hardware button for wifi, 900x1440 12" screen et al) instead of the - now old - 15" MBP with 900x1440 resolution, 34mm expresscard slot and ... well, that's it.. Oh, and unlike any semi-comparable MB("P"), the X200s have a matte screen
With regards to the 12 incher. Well, I never really considered it "pro", but besides a slower processor and lower resolution (all of which is attributable to the way tech were at the time) I consider it more "pro" than the Air and for most intents and purposes more "pro" than the modern day 13" MB.
Glossy, of course, plays a big part.
I have to say, though, that in this day of age you couldn't make do with what the 12" had even if you did indeed up the resolution and the CPU. It would need to take useablity from things like netbooks, X200s, X301 and so on.
Not that they ever will do such a thing, mind you.
Edit:
Bingo. For me the 13" pro is the perfect combination of power and portability. I'd love to have the power of a 17", but I don't want to have to lug around a 7 pound coffee table with me everywhere I go.
That reminds me:
I think we all put different connotations into the word "pro". To some "pro" equals "speed of cpu", to others it means "usability in the field".
I'm in the latter camp. CPU-power is not the end-all to me. Not by a long shot. I don't mind a bit slower, if I can work longer, can plug the things I need into it, and can do what I want and need to. Preferably without worrying about breakdowns, bumps, forgotten adaptors and card readers, wifi-extenders, incompatible FW chipsets, shifting position to not be annoying by my own reflection and what have we.