I've just discovered Mplayer on osx and so far it has proven to be the most capable player yet, playing more files and with greater efficiency than even VLC. For example, an HD XviD video that is 1280x720 is not even watchable with VLC (QT? HAHAHAHA!!!!), but in Mplayer it plays great - granted, with wide sweeping pans it will drop a frame or two but totally watchable. So that is a good thing.
However, my problem is that whenever I open the preferences, the video window and control split for some reason, then I can't watch fullscreen without the Finder menu at the top. Only way to have functional fullscreen again is to trash the preferences and start over - just remembering never to open the prefs again. Is this a typical issue? I know it's not "all there" yet, but this is a glaring problem on my machine.