But you have disabled sync to vblank in Compiz have you?On my 5770 still the same extreme lag when scrolling chromium, and firefox maximized on my 1080p display in ubuntu 11.04. This is with tear free enabled, which really needs some performance improvements, at the very least when it comes to 2D rendering, which for non gamers is 99% of what they are using, and even gamers are probably using 2d rendering most of the time they are on there computer anyway.
Anyone using chromium I found a workaround for the terrible scrolling lag I just described, type in about:flags into the address bar, and enable the the option: "GPU compositing on all pages". This works very well other than some very occasional very minor rendering mistakes that comes with it being an experimental feature of the browser (I'm using the dev build of chromium and it has the option, not sure how long its been there and what releases its in).
Personally I went back to the free drivers using oibaf's ppa, which work perfectly for 95% of the tasks I ever do on this box......the experience is seriously so much less of a headeache than dealing with catalysts constantly changing issues. If dynamic power clocking worked right, there would really be no reason to ever go back to catalyst