I'm running the same. Tried compiling a git radeon two weeks ago. I also compiled the git radeonhd and it's really messed up. Menus drop down but don't redraw background, xv won't work, gl is unusably slow, gl2 flashes wildly etc. So far the best driver I've seen is the straight radeon. I don't care that much about fancy rotating desktops but when I do enable them I see horrible tearing in ALL video output. My definition of "tearing" is when the update is interrupted by a second update. I'm running a 2 Ghz Core Duo that runs flawlessly under Vista. In fact I can't get it to tear no matter what I do.
My primary machine is running Ubuntu 8.10 with the in-box open drivers on an X1950PRO (ie rv570), running Compiz with wobbly windows, rotating cube etc... No artifacts or problems that I can see. Haven't played any DVDs though, just video files including some high-def H.264 files (eg Big Buck Bunny) which all play very cleanly. I have a fairly recent quad-core CPU though, maybe that is helping.
I'm currently running radeon rather than radeonhd because the radeon package on 8.10 works properly with 3D while the radeonhd package does not, but I'm hoping to get the latest radeonhd built and running later this week.
So, how do I install it. I'm familiar with compiling and I can do a git get but I can't find the correct url to fetch it. Can you post the url, I'd be happy to give it a try.
The patch blocks all rendering activity until the next vblank. If your primary use of the system is for video playback this isn't a problem, but it does slow down 3d and some 2d drawing. Alex was pretty clear that this would probably not make it in as a general purpose solution, just as something which would help users whose primary application was video playback.