The most important point Silver makes about the post-debate polls:

How much will the debate move the head-to-head polls between Mr. Romney and Mr. Obama? Actually, the instant-reaction polls may not be very much help in answering that question. The relationship between the quick-reaction polls and their eventual effect on the horse-race polls has historically been very modest, and has sometimes even run in the opposite direction of what the initial polls suggested. Debates sometimes look different in the rear-view mirror, depending on news media coverage, YouTube and cable news highlights, word of mouth, and subsequent developments on the campaign trail.