Now that I think of it, Rudy's best moments didn't come during his "turn," they came when he interjected himself. For example, after Ron Paul's comments, Rudy basically stepped in (out of turn) and criticized him. Any of the candidates could have done that -- but Rudy was the one who did it -- and I think it showed leadership. Candidates shouldn't be obsessed with following the rules of the debate or appearing not to be "polite." Was it polite when Ronald Reagan said, "I paid for this microphone...!" Rob Bluey makes the point that: "If Giuliani goes on to capture the nomination, his response to Ron Paul will be one of the moments that is replayed years from now."
In terms of McCain, it seems to me that he's being very disciplined, in terms of staying on message. He's got his sound bites that he wants to get out, and every question is answered with a canned response. The positive thing about that is that you control the message (and avoid gaffes). The downside is that it is very boring (especially to those of us who follow this stuff closely). Luckily, for McCain, average voters spend only about 7 minutes a week thinking about politics. By repeating his lines over and over, he is assuring that average voters will eventually absorb it.