I'm using the latest cataclyst for the 4850 and it works fine almost all the time. Sometimes when I switch between a Game and Windows Desktop there is this "split screen issue" where the upper half of the screen becomes the lower one and vice versa, but that's it
Follow the Vista instructions further down the page but you don't need to disable UAC in Win7 as it's a smarter UAC then Vista. Works great and then you'll have the Catalyst Control Panel as well. Cheers!