There are only a few bugs known at the moment, none of them are critical. That's very long gui startup time when you have many files on your memory card and audio/video sync problems which are not quite clear yet (but variable audio bitrate is a suspect). If you encountered anything else, it would be nice to report it providing all the necessary details that are enough to reproduce the problem. As you may guess, "buggy as hell" can't be considered an informative bugreport and provides zero information That's a Media Converter thread and it would be not very nice to hijack it, reporting mplayer bugs can be done at garage trackers : https://garage.maemo.org/projects/mplayer/

That's true, MPlayer suffers from tearing more than the standard video player. It's a price it has to pay for better performance and playback without freezes with the current firmware. When a fixed firmware gets released, MPlayer will be tweaked to do its best on N800.