Be careful, as a medical school interview is quite different than a job interview. Most job interviews, for instance are focused on technical skills, finding out experience, etc., whereas a medical school interview is to get much more of a holistic look, and as you said, determine one's level of humanity/charisma.
Baylor College of Medicine was my first interview, but I did interview there early (first day). The interview didn't go horribly or anything, but now with 6 more interviews under my belt, I see it could have gone better. I did get an acceptance at Baylor. University of Michigan was my second, I would say it went better than Baylor. The student interview was fantastic, but I'd say the faculty interview was a hard read and could have been more excellent. I got accepted at U of M. I knew my Michigan State interview went Horrible with the student interviewer (he was a really awkward M1), but okay with the faculty. Haven't heard back from them...
I guess I haven't had enough feedback from schools (no rejections yet) to fully forumlate a better idea. I do think that we overestimate how well interviews go, though. I don't think the process itself is a craphshoot, but I'd say an applicant's evaluation of one's own interview is.