You know, I think the ultimate problem with Reddit was the fact that the arrows had no clear name. People gave them the name "downvote" and "upvote". That ultimately lead to their misuse. The simplicity of the feature allowed users to define for themselves what they were for. So while the original idea was people could "vote up" for good "quality" of content. People ultimately ended up using it more for "things they agree with". Its the source of the hive mind.
That said, it still worked fairly well. I think there's something to crowdsourcing the problem of finding the signal. If I was to try and improve the feature, i'd add one more step the process. If a modal window allowed users to designate WHY they were doing the action, it might cut down a bit.