I guess if you've read On the Historicity and the standard rebuttals against it you won't find too much new, but worth seeing it played out in debate format.
This was my youtube comment which I'll simply copy and paste:
Fantastic debate. Horn definitely exposed some of the weak points in Carrier's argument. Was good to see Horn go straight for the jugular attacking Carrier's views head on in his opening. I was expecting a lot less from the rent-an-apologist. Carrier's rebuttals were fantastically detailed and showed that he is not some quack conspiracist (which many mythicists fall into). The line "possible but not probable" was thrown around a lot in this discussion by both, and I mostly felt that it was Carrier's views that were falling into that category. Carrier makes the best "possible" case for mythicism, but even as an atheist I have to concede that the more straight-forward and thus likely reading of Paul is that he believed Jesus had been here on Earth (even if he also believed him to be some incarnated angel or what-have-you). Carrier has stated that he wants to debate Mark Goodacre in a proper formatted debate like this (forget their brief radio interview a few years ago). Goodacre is one of the top scholars in the world, no rent-an-apologist, and after seeing Horn's not-disastrous performance here, I fear that someone like Goodacre might be too much to handle. I would love to see that debate happen. To bad Ehrman has stated that he wants nothing to do with Carrier!