Have you ever seen StackOverflow? I think vote up and vote down sites work great for when attempting to determine what is the best answer (wisdom of the crowd and whatnot). I personally don’t think it works well for discussions and debates. For myself, here an upvote only system for members seems best.
It might be interesting to add a critique system. Something along the lines of allowing member to flag feedback (informative, valid argument, PotM, etcetera).
An interesting variation for voting might be to have people programmatically declare sides and then only let them vote for people with similar enough views to their own.