Some time has passed since your prior posts to recently.
I think these days that xv does work with radeonhd. I use xv and radeonhd to watch dvd movies and have for some time using xine and mplayer. This is with slackware 12.2 and slackware 13.0 (32 and 64 bit). I can't imagine it doesn't work with fedora or others.
Yea, there was that goofy fix for mythtv about changing the screen by one pixel or something like that. I don't have to do that anymore.
Mythtv works ok for me with slackware 12.2. Slackware 13 used qt4/kde4 and mythtv doesn't work with that yet.
Edit: I have an integrated hd3200 so not identical to yours.