I really wish some of these high resolution laptops came with equivalent high end video cards to drive that resolution ... shipping with a 750m rather than the 780m seems nuts, it is 2 to 3 times slower and when you got 5.5+ million pixels to drive...
The 780m is a huge power draw. It's basically a minorly downclocked GTX 680, with all of the performance (and heat) that implies. It's estimated to draw 122W at maximum, for crying out loud! It probably won't be fitting in a .7" laptop anytime soon.
Aside from that... This laptop isn't intended for gaming. Honestly, I'd think that if Intel HD graphics can drive an rMBP display, then the 750m will suffice for this. Though I would love to see QHD+ come to some of the gaming laptop lines...