Light siders can use dark side powers. I'm still playing light side, so It'll be a while before I do it again, but I'll do dark side then. While I normally don't play "evil" at all, or if I do I play it in such a way that I do good things to deceive the goody-goodies and get better prestige/awards. However, in this case there is a world with a Sith training facility, and there is a HUGE storyline spoiler that makes Dark Side a perfectly appropriate selection to play.
