I really like the idea of an apprentice, it sort of gives a more active version (though of a different nature) of the Revan-Bastila bond in the first game and given how that (in some way) will hang over this game it creats good depth, more RPG than hack-n-slash, better cause-effect and good continuity with the first game.
You are after all a guy/gal who followed Revan off to the Mandalorian wars and then esp. of you go LS, you have a good mirror to the Sith master/apprentice realtionship.
Someone earlier mentioned romance between them.....well that would be interesting, given obviously not only the Jedi (and SIth) codes views on love but also how it relates to a master/student relationship.