I've been trying this since I did back it after all and well....almost done with Sagus Cliffs (I think) and I'm getting the same feeling I get when I play Bioware games, as in I can act like a complete dick or mustache -twirling villain to any companion or NPC and not even think twice about it, not because I really want to see what happens but because I'm just not seeing the characters beyond the pixels.
Compare this to Ps:T where every time I replay it I'm thinking:'Okay, this time I'm gonna try the evil path, I'll lie, kill innocents, give away Morte to the Pillar, sell Dak'kon to slavery, hang around with Ignus...' and then 5 minutes in I stumble on Dehionara
... So far I've never been able to play through Ps:T with an evil Nameless One.