I learned that this is Dan's eighty-seventh (!) public debate and his sixth with Dinesh. He said he spent about a month preparing for it, even going so far as to re-read Dinesh's book, What's So Great About Christianity, which is somewhat related to the debate topic of "Is Religion the Problem?" He said that when he's talked privately with Dinesh, he's fairly nice and definitely a true believer. Apparently Dinesh accepts evolution and condemns biblical literalism, and seems to believe in an eclectic mixture of Christian doctrines. From what I've seen of him previously, his debating style seems superficially cordial but unpleasantly slick.
Dan had some insightful things to say about the debating format as well. He said you could spend a lot of time preparing for debate, but you may use very little of that preparation if your opponent raises unexpected points. In terms of dealing with ad hominem attacks, he said one can tell the audience explicitly that the opponent can't counter the arguments, so he's making character attacks instead.
I got to hear a few funny debate stories as well. Dan mentioned a debate in which his opponent asked the audience to close their eyes and "feel the Holy Spirit" while he played three minutes of religious music. In response, Dan identified the patterns of notes within the piece of music and said that it was an arrangement that composers often use when they want to evoke strong emotions in the listeners. "It was a very pretty piece of music," he'd said, "but I didn't feel the Holy Spirit." I've heard plenty of appeals to emotion before, but never such a blatant and extended one in a debate setting.
The head of Rational Thought, Jonathan, also told a story about a debate he'd had where after a series of questions, he got his opponent to admit that he fully expected a scab on Jonathan's arm to be healed through the power of prayer. The opponent and several of his supporters prayed over the scab for a full minute, and when (surprise!) it failed to heal, the opponent said, "Well, does it at least feel any better?" After the debate he seemed bewildered that it hadn't worked, suggested it might get better in a day or two, and told Jonathan he'd keep praying for it.
We discussed free speech on college campuses, religion in politics and several other topics as well. It was a great experience overall. I wasn't planning to attend the debate due to a prior engagement, but now I think I will unless I get confirmation that it's being filmed.
Update: It was being filmed. I went anyway. Will comment later.