I'm running a Radeon Mobility X700 (Gallium r300g) glxgears gives a solid 60FPS, synchronized to the refresh rate of the monitor. Holds at 60FPS when KWIN effects are enabled. Granted, I don't enable many effects other than the absolute basics. KDE 4.8.4 gives you a lot of control over which effects you want to run. I think this bug can be closed out.