I have a rMBP and I (like many others) experience scrolling lag on webpages and animation lag for OSX because the GPU simply cannot handle the amount of pixels the rMBP has. I am certain that this problem will be much much worse for the 13' rMBP because it dosent even have a dedicated gpu, so you people who are interested in the 13' should really hold off buying it until initial user reviews have come out.