Running stock mini 9 ubuntu here with a00 bios. Whilst it isn't perfectly resolved yet, I am getting close to good quality un-choppy 720p playback.
I used synaptic package manager to install the mplayer no-gui version. Then from a Terminal window doing something like "nice -n 0 mplayer EU_RD_GRID_EUROPE_trailer_720p_01.wmv -fs -really-quiet"
I'm finding the video playback to be good with few dropped frames, but better than that, no pausing of the video. Instead it's the audio that cuts out for approx. 0.25 in every 2 seconds but doesn't lag behind the video.
No bios upgrades, cl4 memory, or zappier ssd
's here so might be better if I can get those done. I'm holding out hope this can be overcome. The audio suffers more if I'm running resource monitor in the background so things that will minimise traffic on the bus is going to be vital I think to squeezing out that last bit of needed performance. Better codecs might be the deciding factor too, just have to hunt them down and try them out.