Which rMBP model do you have?B... : I just tried all that and I also have a 15" cMBP [ AG + HR ] with the same specs [ except the SSD part] right next to each other today, [ both are mid 2012 models ] and I see zero lag on the rMBP.
I'm comparing both and the rMBP is just as buttery smooth as the cMBP.
I have, however, seen lag on a few rMBPs [ using Mission Control, and resizing the App Store ] that I played with in the Apple store. So, it isn't as if this *lag* is a myth!
I believe, some rMBPs are plagued with this [ along with the dreaded IR on those LG screens... and the EFI update bug.. ] while others aren't.
To me it is evident when you have 2-3 windows open and try to activate Mission Control while using the integrated Intel HD 4000 graphics (one of the reasons I'm waiting for Haswell).I have a 2012 Macbook Pro, 15", 2.7GHZ, 16GB ram, 512 GB hard drive
I cant find an instance where I get the UI lag people talk about, but I would like to see if I can
I think Webkit is making the scroll on zoom much better. Definitely no lag while normal scrolling anymore, and that used to be a big issue when I first got my rMBP last summer. We will get to complete smoothness one day!Safari: zoom in then scroll.
Calendar: flip through the month page animations
Resize the app store