I've installed this driver on my Gentoo system with rv770 4850 graphic card. Performance in KDE4 apps (dolphin, plasma) is great, but only witch enabled composite (by running xcompmgr). Without composite enabled, moving windows is very slow.
But I've noticed a problem - i can't enable XRender-based desktop effects in kwin configuration window - it displays standard dialog without any usable information (it says that activating windows effects failed). Xcompmgr works without any problems. Any ideas how to force kwin to worh with experimental r600/700 radeonhd driver? I've tried "disable functionality check" option without any success.