The current status of my work is at git://people.freedesktop.org/~anholt/xf8
The code is mostly the same as what's on the branch, with just some changed buffer handling that should be all-or-nothing rendering correctness, not brokenness with colors. If I turn on xcompmgr, that desktop background goes thoroughly flourescent, and the windows partially translucent. Something very weird is going on, and I'm going to take a break and fix my 830/845 Render performance fix ("here test my patch, oh wait I didn't make it compile first") instead of bashing my head against this for now.