Nobody won the debate.
Depending on what areas you evaluate their performances each scored points and made mistakes. McCain never looked at Obama, he appeared to be dismissive and condescending. Obama seemed long winded and lecturing at times making it hard to focus on the points he was trying to make. McCain's refrain of 'Obama is naive, inexperienced', "he doesn't understand" was used a little too often and came across as a an attempt to create a catchphrase instead of underscoring the areas where Obama was weak. Obama's use of "John is right" detracted from the attempt to point out where substantively McCain was wrong.
McCain's rhetoric was clearly stronger when actually discussing foreign policy. He appeared self assured and comfortable when making his points and the declarative admission of never allowing the US to torture prisoners again; the first time IIRC that someone in the Republican party has actually admitted in an open public forum that the US has "tortured", was very powerful.
Obama's strength was to provide more substantive information clearly and concisely. He opened with 4 detailed points for the bailout plan delivered facing the camera and effectively looking the American public in the eye. Some of his facts/information was inaccurate but he was factually correct more often then McCain in all areas. When he told McCain he was "wrong" or pointed out what he was saying was "not true" Obama's rebuttals were factually correct.
McCain's overall body language and demeanor communicated his personal dislike of Obama. He was unable to hide that he was there under duress and would have rather been anywhere but on that stage with Obama. I feel this reflected poorly on McCain; while he was able to keep his infamous temper in check, I have to wonder if he would display the same type of demeanor and body language if meeting with heads of state with whom he fundamentally disagrees with or dislikes. He doesn't need to win "Miss Congeniality" but he should at least be able to appear congenial.
In contrast, Obama came out open and smiling with his hand extended. He appeared attentive, thoughtful and actually looked at McCain once Jim Leher admonished them to speak to each other. There were a few times he stood with his head down while McCain spoke forcefully during an exchange, giving him the appearance of the youngster being taken to task. Overall, I would say his body language and demeanor reflected confidence and self assurance.
The debate was a tie, however, the advantage always go to the person with momentum and in this debate that is Obama.
The next two debates are set in different formats and will, hopefully, allow them to demonstrate clearly why they would be the better President. This debate simply was not what was needed to help anyone who is undecided.
Boo
FWIW, I am voting for Obama and had decided to do so during the primaries.