I currently have the MacBook Air 11" and previously had the old unibody MacBook Pro 15". I really want a 15" rMBP (main thing I want is the dedicated graphics card, plus the large screen and also the retina display) but I am concerned about the weight and portability of it. My old unibody MBP was a tank and quite hard to carry, frankly. Any advice regarding the portability of the current rMBP? (Quite hard for me to tell when the rMBPs in the Apple stores are chained to the desks.) Thanks.