There's still lag if you go to image-intensive sites like theverge, but it's mostly fixed on other websites (like the Apple website).
BUT
I did notice a slight jerkiness when you "overscroll" and the screen slowly comes back to the the regular spot. It only appears if you overshoot considerably, though.
Bottom line: It will shut up 99% of the complainers. Unfortunately I happen to be in the 1% (that's not to say I'm grateful for this update, I'm just concerned if this means it will be the last update for UI lag on the rMBP).