Some quick thoughts from me:
--Hitchens absolutely won the debate. It wasn't because he made the best arguments one could possibly make on the "no" side of the issue (I think others have made better ones), but because D'Souza really phoned it in tonight on both the logic fronts and the common courtesy fronts (ad hominem was the order of the day from the "yes" camp).
--I find it rather interesting that, in this particular debate, the "yes" side (D'Souza) attempted to use material-world analogies in order to explain metaphysical-world realities, without noting the irony in their being irreconcilable. The fun thing about these analogies is that as soon as you apply the realistic framework of the world all of us agree exists (with the exception, perhaps, to those philosophers who try to argue that maybe we don't exist, or know if we exist, and so on) to D'Souza's arguments, they fall apart entirely. It's like saying "I'll talk about this apple as though it were God" without realizing that your audience can see the apple, but cannot see God.
--There were a few crazies during the audience Q&A. I suppose that shouldn't be a surprise, but I thought it was great that Hitchens (and D'Souza, sort of) took the attacks launched at him in stride. He's been at this long enough, obviously (not just with religion, but with a host of other controversial topics), so he knew exactly how to deal with such things.
--Hitchens and D'Souza are both quite good at making jokes about their respective opinions and the other side, and in good taste. I was happy about this fact because I think if they had been more mean-spirited it could have turned out nasty for either side (during the debate and from the audience). The audience responded fairly favorably on both sides of the issue, actually.
--People who get into the line for book signings should have a book to sign. Hitchens got a little upset with this couple who tried to hand him a card instead of a book...I did too, because I wanted to thank Hitchens and D'Souza for the talk, but apparently Mr. "I can't be bothered to show up on time to get a copy of the book" had to ruin that moment.
Overall, I think the debate went rather well, despite the fact that D'Souza seemed very much out of his element. His arguments seemed sound if you didn't think deeper about them, but the second you took that extra step (as anyone, religious or otherwise, should), most of the arguments fell apart or could be directly refuted by historical or scientific evidence (D'Souza did get a few facts wrong, unfortunately, which did not win him any favors from Hitchens or some members of the audience, religious and otherwise).
Now all I can hope for is a debate between Dawkins and the guy who runs the Discovery Institute. That would make my year!