Fine tune? It doesn't even coarse tune. I'm using gnome 3 at the moment and it allows me to set my preferred media player as VLC over the default Totem... but it won't bother using that setting and cranks up Totem every time.
Also, rather humorously, the 'preferred applications' part is hidden behind System Settings > System Details > Default Applications. News to the Gnome folks: user app preferences are "Personal" not "System" (using their own terminology). Unless, of course, my selection here changes all users' settings... which would be equally insane.