That was a much more even debate that the first one (where Romney was the clear winner).
I think Biden will get some negatives for his aggressive and interrupting style, but he scored more debating points on Ryan. Ryan was fine on tax and domestic issues, Biden did much better on foreign policy and soft issues like abortion. He dodged the part of being a Catholic and supporting abortion, but it is credible to do so in an era where you can point to Islamic extremists forcing their religious views on their citizens.
I think that the abortion question was a defining one as in it provided a clear choice to voters - vote for me and protect abortion rights or vote for me and I will oppose abortion rights. Coming right near the end of the debate and with Romney behind and needing to pick up more votes, I would say that public opinion and women voters would be much more in line with Biden's offer than Ryan's.
I lean towards a narrow Biden victory in that debate with that one telling passage right at the end.
Michael
(I am pro life but not pro pushing my faith and emotion based arguments onto the population at large. I have no issue with not spending federal dollars on abortion. I do have issue with eliminating it as a safe and legal option for women, regardless of how they became pregnant)