So interesting to hear this all the time: "it's a software issue", "it's a software issue", "it's a software issue" - since day one this has been the standard answer regarding the laggy retina machines..... and STILL Apple has done nothing to fix it?!?! Well, maybe too many pixels still is to many pixels for a thin portable machine...?
I think what the "it's a software issue" people are trying to say is, out of the box, with a clean setup, they won't face this problem? So looking to get more users to chime in here.