I have returned my 13" 2.4/8/256 due to the screen size and UI stuttering under heavy load. People always talk about how the dgpu is only good for gaming and video rendering but wouldn't the 2gigs of GDDR5 on the 750M take a load off the system and let everything run smoother? Also, I think I read somewhere that the Iris pros Crystelwell 128mb of L4 cache can be utilized when the dgpu kicks in but I haven't heard what real world benefits that would provide. Will the dgpu of the 15" improve driving the retina display and an external display while multitasking Photoshop, Illustrator, Indesign, Dreamweaver, VMs and browser tabs galore? No gaming or 3D rendering needed.