I'm not a fan of any karma or like/dislike buttons. I feel that it's obvious enough from the feedback of your post on how others feel about your ideas. There's already been enough trouble here with disagreements, so it's not worth it in my judgment to add such a feature that could spark up even more trouble.
I would rather see everyone provide good explanations into why you agree or disagree with someone in a non-confrontational style. It's okay to disagree with someone provided that it's done in a civil manner. This approach adds more substance to the topic, encourages useful feedback from others, and keeps everything moving in a friendly matter. Besides, if you really need an opinion, use a poll as everyone's vote is anonymous unless someone tells us in a post. Please don't overuse this feature if you decide to pursue this route.