All things considered, I rate this debate as highly as any of the other Democratic debates, largely because the YouTube questions did not come from a member of the media. It may have been just The Wisdom of Crowds generating better questions, but the format conferred two advantages. First, candidates were under more pressure to address the specific question being asked to a greater extent than in prior debates. Being dismissive of Anderson Cooper doesn't cost a candidate anything, but being dismissive of "ordinary" Americans wouldn't score any points. So the video asks, and the moderator can follow up. Second, it is easier for Anderson Cooper to cut off debate on a stupid question from a YouTube video than (under the traditional format) if he had asked it himself.
From my own vantage point, I thought that, as in previous debates, Senator Clinton entered as the frontrunner and didn't lose any ground to her principal challengers (Obama and Edwards). It will be interesting to see when (or if) Senator Obama starts to draw sharper comparisons in order to close the gap. Of the remaining candidates, I thought Senator Biden made a good showing, particularly on questions related to foreign policy that played to his considerable experience.