Both candidates needed to do certain things, and both did. McCain needed to stick to the talking points and not get too irritated or condescending. He needed to avoid a major error in fact. Obama needed to look presidential, speak in short, clear sentences, and not get irritated.
So fans of both candidates could be happy -- except that McCain's campaign is currently cratering. He didn't need to hold sway, he needed something that would turn the election around. He didn't get it. Worse, if you were leaning to Obama and tuned in just to see if he passed the smell test, you'd be pleased. A tie is a pretty big win for Obama.
Sometimes I think we over-analyze, too. Obama really does hold all the cards. In reality, this was a low-stakes event because he knows the issues and is right on them. It was far worse with Hillary because they agreed on everything. We had to start going to the tie-breakers to see who won, subtle things that are the height of subjectivity. But McCain versus Obama is night versus day. They don't agree on anything, and America largely agrees with Obama. As long as he didn't start jabbering incoherently, he was going to seem more reasonable simply because the guy you agree with always looks more reasonable. And most people agree with Obama.
A final point is just how much Palin may have damaged McCain. By tossing out someone who actually has no experience and demonstrates it, he has given America an object lesson in what inexperience looks like. And Obama doesn't look like that at all. In a perverse way, McCain has made the best case for Obama's experience by selecting Palin. This was thrown into sharp relief when, following Joe Biden's appearance on two networks (at least), announcers had to say that Palin wouldn't show. She couldn't because she's not ready. It made Obama's performance look less like stagecraft than actual knowledge--something Obama was having a hard time proving on his own.