I support the idea of a Helpful post button because it adds a qualitative dimension to the post counts, titles (Evangelist, Legend), and program affiliations which members may use to assess a post's credibility. Positive reinforcement encourages more of the same, and this tool should increase engagement of members who are high quality, but infrequent, posters.
We already have a triangular Unhelpful button, located in the lower left corner of every post.
I don't think TalkBoard's role is to simply follow the results of a poll, but the number of members who have voted in the poll approaches the number who voted in the most recent TalkBoard election, and it should be given some weight.