not on my computer. I use XINE or VLC but almost never mplayer. I've just personally had problems with dvd playback although I don't necessarily blame it on mplayer. It just seems that my video card and sound card flaws show up when I'm using mplayer and not showing up when i use xine or vlc.
PS: I'm assuming mplayer is the player of choice for playing dvd on FC2, right?
Still, as a backup i'd install xine and vlc along with mplayer.