I was teaching the diocesan bible study & apologetics courses last night, and hence only caught the last ten minutes or so of the debate, and that on the radio.
Based on what I heard, I thought Kerry did a slightly better job. I spoke with my wife, and she thought Bush came off better on TV than on the radio.
From what I've seen, it sounds like the consensus (among both sides of the aisle) is that it was a narrow Kerry victory (although a few think it was a draw, and some think Bush won). Quite a few folks think that Kerry needed a knockout, and hence his narrow victory was insufficient. While I don't think he scored a knockout (based on what I heard and what I've seen after the fact), I do think this debate was helpful to Kerry, although there's room for debate about the extent of the help.
One thing, though: one of the questions I caught pertained to Russia and Putin (can someone teach George to pronounce "Vladimir" as "Vladimeer" and not "Vladimer"?). In his time, Kerry noted how shortly after the fall of the USSR, he saw all the files in KGB headquarters, underneath Treblinka Square.
There's a little problem... Treblinka was a Nazi death camp! Kerry was referring to Lubyankaya Square. Now, that's really not that big of a deal. But somehow I suspect that if the President had said it, we'd be hearing a lot more about it.
In spite of that gaffe, I still give the debate to Kerry, slightly.