I'm a grizzled, jaded, seasoned design guy who's owned 15" MBPs for years. And I've spent nearly every work day with those 15" MBPs tethered to an external monitor. Now in the market for a new MBP and wondering, Why not buy a 13", given the fact that the 13" is almost always a secondary monitor, save for the rare times that I actually use the laptop by itself, sans external monitor? Any other design (or related) folks ever been in this position? Have an opinion about sticking with the usual 15" versus downsizing to a 13"?