It's hard to tell from the gloomy marketing shot, but the Apple logo is about 1.5 inches wide on my MacBook Pro. From that, this machine would appear to be under 13 inches wide, which would suggest a 13.3" diagonal. The edges, however don't look at all like the MacBook Air.
I miss the 12" PowerBook. You do too. Is this a happy moment, or rose-tinted pixtacles?
Maybe! For reference:
Apple announced October 14 notebook event in Cupertino [Ars Technica]