I had the retina pro since 10th july, using it for hours everyday for reference its the 2.6Ghz 16gb version with 512gb HD Before i owned this i have had other macbook pro's, air's and the old ibook! so i have had a fair share and would think that i would be able to shot this lagg but i cannot! People are constantly moaning about it but i just cannot see it, and i am quite picky with stuff like that. Some of my friends computers / laptops lagg like a piece of **** and it grosses me out. TLR: I cant see any gui lagg, where is it!