A big thank you to the devs!
After building kernel 2.6.31-rc8 & dri2 & drm & mesa & xf86-video-ati I have beautiful 1440x900 accelerated framebuffer and 3d on my 1st gen Macbook Pro (AMD X1600) running Debian unstable. Compiz & Google Earth are behaving as advertised. No artifacts with video playback!
The only hiccup was in xf86-video-ati (I had to change DRI2BufferPtr to DRI2Buffer2Ptr in radeon_dri2.c).
After waiting for 10 years I now have an unified video driver in Linux and it is a wondrous thing. Again, thanks!