I just installed RockBox on my M3; I don't have any other choice but to use it actually, as the default firmware refuses to recognize the CompactFlash card in the CF to IDE acapter I got to replace my dead harddrive (reads the firmware from it though).
Problem is, when I play a song, the screen goes all funny like there is some sort of interference running over it, and most of the time just goes blank after a few seconds. It keeps playing songs fine though, and listens to the controls for next and pause and so.
I really hope we can work on a fix, because I can't really use it like this...