Just to go back a bit, I second
@Goro'a response to your question. Significant conversation is typically reserved for applicants that have a wide variation in their pre-interview scores (we actually report means with standard deviations - go figure) and applicants that are "on the bubble" in terms of reaching our threshold score. Applicants that are either clearly going to be accepted or waitlisted or those that have little variation in their scores usually don't get much discussion. We have two hours to talk about 15-18 applicants. For the "quick" applicants, usually the committee member will just present them (i.e., essentially summarizing their application and hitting the key points for the other people on the committee), and if anyone has any final comments they'll provide them after the presentation. That kind of applicant will typically take no more than 3-4 minutes. For the more "difficult" applicants with some room for discussion, we might spend 8-10 minutes discussing them.
At my institution, we highly value interviewer comments. In fact, when I'm looking over an applicant, I'll typically read their personal statement, secondaries, look at their numbers, and then go straight to the interview comments. It usually takes 15-20 minutes to read through a file, so if someone has a really poor interview then they're likely sunk and I'll just skim the rest of the application. Not every school places that much emphasis on the interview, but our thinking is that applicants have already been screened for interview invites before we see them. Thus, it's extremely unlikely that we'll get someone who is a straight-up "poor" applicant. Don't get me wrong, our process is still holistic and we still take the whole application into account, but generally bad comments from interviewers can sink an applicant that is otherwise outstanding on paper. In fact, at our meeting yesterday we had two applicants that fit that bill exactly - applicants that had a 3.7+/35+ for numbers, great ECs and generally strong letters, but weird interactions with interviewers that gave off a bad impression.