Things to consider:

1) Only registered members can vote and they can only vote on each post once (need to add userid with each post and then check for duplicates)
2) Members profiles includes their average rating
3) A page that lists the top ranked members

I think perhaps some link to the "auto ignore" mod people have been talking about. Ignore people you dislike thing where their posts just collapse into a single line and you do not get emails when they post.

I would personally make the ratings all positive. If you don't vote then you don't think the post is that good. So like

1) = useful, 2) extremley useful 3) Perfect

something like that. Maybe enlarge to 5. I guess this would be left to each person to decide.

Just some ramblings. What do people think?