No knockout punch delivered but given that he was actually debating two people, I think he did just fine.
Not only did President Obama come into the second presidential debate more aggressive and prepared, but he brought a secret weapon -- the moderator, Candy Crowley. At two pivotal moments, Ms. Crowley, typically a relatively fair reporter, showed her bias and changed the course of the debate.
First, she backed up Mr. Obama's assertion that he had called the attacks at Benghazi a "terrorist attack" in a Rose Garden event on the day after the tragedy. (After the debate, she reversed her assessment and stated that she was in error.) Second, she consistently let Obama stay two minutes ahead of Mr. Romney in terms of time, and at the end of the debate, Obama had a full three-minute advantage. In addition, at the end of the debate, Crowley gave Obama the last two minutes for a peroration where he gave new arguments (including the "47 percent") without fear of rebuttal.
Further, throughout the debate, Crowley thanked Obama for his remarks with a very deferential "Thank you, Mr. President"; she merely turned away from Romney at the end of his time. Thus, the town hall-style format ended up being a three-way debate, with Romney facing two opponents.
Even against those odds, Romney came away the winner. Obama improved his performance and clearly was more engaged in the second debate, but at best, he tied Romney on content and lost significantly on delivery and style.
I was hoping for the KO but fell asleep believing that Romney will continue to see the undecideds swing his way.