I have been running Mythtv on my 790GX system for 6 months now on a 1360x768 LCD TV. It plays both analog and HD video with very few problems. (The only problems is when viewing HD and having some of the Myth program overlays fading in and out, the screen gets a little choppy.) I used to compile drm from agd5f, but now I just use the 2.6.30 kernel drm. I'll patiently await 3D support and test it on my other system (with an HD 2600 Pro) before I apply any major changes to my Myth system.