My impression of the reputation rating is that if the poster makes a solid post, you give him/her positive points. That would make sense, however you have people giving rep just because they like the poster or taking away rep because they hate the poster...it's hard to control, however looking at who is on top of the rep chart, Greg and Paul specifically, the ratings have not gone too far off the mark.
The only other way to do this is just have Marty give rep to members..