Last week EXA improvements were added to the CS branch of this open-source ATI R500+ driver by means of hardware-accelerated downloading and uploading from the screen. Now committed to the development branch for this driver is acceleration for EXA Composite and Render extensions. Additionally, a few other improvements and other work (setup code for the 3D engine) was committed today.
If you're interested in checking out this latest open-source work checkout git://anongit.freedesktop.org/git/xorg/driver/xf86-video-radeonhd and then proceed to checkout (using git) the origin/CS branch. TexturedVideo code for the RadeonHD driver is expected this week and there may be a new official RadeonHD driver release later this month.