I come from MBA 2011 so I don't know all the fuss people have been talking about the scrolling lag issue in retina models. I'm considering to upgrade to the coming rMBP Haswell line so that bothers me a lot. What lags, besides Safari? Has the issue been addressed in Mavericks beta? Is it the fault of HD 4000 being too weak to handle the resolution? Do you think the situation will be any better with Iris Pro 5100?