I have a Radeon HD 5450 graphics card. Running Ubuntu 10.04. When I install the proprietary graphics drivers I get good video rendering (YouTube) and appropriate screen resolution. But when I open a browser window and scroll or move a window around I get terrible lagging which drives me nuts.
I now run in low graphics mode. I get poor video rendering and poor screen resolution but no scrolling issues or lagging windows. I run in low graphics mode because this is priority for me. I don't watch videos or care what my screen looks like. I just don't want lagging scrolling.