I tried the softdevice plugin today. It worked fairly well considering it hasn't really been designed to output to a TV, which has different sync requirements from a monitor. The A/V sync was close enough and there were few enough frame jumps to make it quite watchable.
However, softplay wouldn't work properly with the XVid files I tried, only showing a few corrupt frames. I'm pretty sure it's an ffmpeg problem because there were similar problems with some things I've been doing myself with ffmpeg lately - I haven't got as far as displaying the frames, but it does seem to keep stalling while decoding and the Debian package version was complaining about "VOP not coded" all the time.
Anyway, I tried upgrading from the Debian libavcodec to the latest CVS, to make sure I don't annoy anyone if and when I report this problem on the ffmpeg mailing list, and then softdevice wouldn't work. It just shows a frozen picture with the initial OSD caption you get when starting to play a channel. softplay wouldn't compile either but I just needed to change . to -> in a few places.
So will there be a new softdevice and softplay compatible with the latest ffmpeg soon?