Hilary held her own and managed to do it while mostly smiling (except when attacking Republicans so I assume those are the shots Faux News will be showing). She came across (at least to me) as competent, smart, able to give as well as she got, and in general like a pro, though I disagree with some of her positions.
Bernie was Bernie, which meant sometimes he said stuff no one else dares or cares to, and sometimes he just repeated himself or seemed a little tired, which is completely understandable and didn't hurt (at least in my opinion) his "image" since his "image" is of an old guy who actually does speak truth to power and isn't trying to project any "image" other than his ideas and beliefs.
O'Malley seemed like he was at a different event for the first half, at least, of the debate (or as the friend I watched it with said, he seemed almost "robotic"). Someone must have advised him to seem serious and show gravitas, a mistake (at least as far as I'm concerned) since I have friends who are friends with him and they say he's a really down-to-earth fun, smart and compassionate guy, which didn't really come across as most of his remarks, again especially during the first half of the debate, were stated as if he were reading a script for a robotic answering machine.
Webb, who I used to find pretty fascinatingly unique in politics, came across (to me) as self-serious, stiff, and talking to himself or insiders instead of the average voter, who ever she may be.
Chaffee actually was disarmingly sweet and human, though he looked on the TV like a cartoon character, maybe a duck or chicken, and despite some great things he had to say and positions he took, was hard (for me) to take seriously as a contender.
Cooper wasn't bad as a moderator, a tough job, but wasn't the best either. But the call-in Facebook aspect of the debate was so incidental they might as well not have done it, and it could have been much more a part of the whole event and more spontaneous, that would have been (for my taste) made it a much more dynamic "show."