Just wanted to chime in on my experience with this. I had learned to live with the scroll lag, as I spend most of my time docked to a TBD anyway, but was still annoyed by it. Especially considering facebook and the verge are 2 of my most visited sites. Last night I decided to do a fresh install of ML (formatted the drive, then download/install). I previously had ML installer over ML DP4, over Lion. The main reason I chose to do so was that i was having issues with power nap and read this could resolve them, and also because I'd heard of people just having generally better performance on a clean install. I'm happy to say that as of now my scroll lag has been reduced almost entirely. It's very, very noticeably reduced. The main pages I used to check are Facebook.com and Theverge.com, my 2 main sources of the lag. This is on the HD4000 and running off battery, in Safari 6.