I was disgusted by McCain's condescending attitude, coupled with his refusal to examine complex matters closely before doling out prospective punishments and languishing in war stories. He also struck me as dangerously impulsive (a blanket spending freeze on nearly everything but defense? Where did that come from?).
I think people expected Obama to score major points here, but he seemed disinterested in point-scoring. Instead of reacting to jibes, he clarified; his attitude seemed almost professorial. He also demonstrated quality of character: addressing McCain head-on, acknowledging valid points (which Rudy Giuliani has already tried positioning as a concession of his inexperience), looking him in the face, and, at the end, reaching out to shake his hand as McCain prepared to walk offstage.
This late in the game, it's foolish to expect either candidate to go out on some kind of radical limb. Who "won" the debate came down to how they fielded unexpected questions and addressed each other. These characteristics will determine how, as President, they will manage bipartisan grievances and negotiate space with other countries on our behalf.
McCain believes in forcing "preconditions" on proud leaders that are angry with us; in contrast, Obama drew a distinction between "preconditions" and "preparation." He believes these people should be acknowledged, face-to-face, and given the opportunity to speak their piece before the US reacts.
A guy like Ahmadinejad isn't going to kiss the US's ass with "preconditions" before agreeing to have lunch. Demanding that he do so is neither respectful of his power nor productive; it's poking an angry animal. That Obama would look him in the face, without reservation, and listen before exercising retribution on his country, speaks volumes about how he can repair our global reputation.
More analysis on The BBC. Also read Fox/AP coverage of big points made.