H I'm currently on the shuttle back to MSP from Rochester and thought I'd pass along some info that might be useful. My apologies if anything has been said before.
As far as the interview day goes, you'll have two interviews of 30 minutes; both will be with members of the admissions committee. There's also some "explore Mayo time" which is essentially free time, and everyone had about ~1.5 hours of this over the course of the day. Everyone seemed to agree that the interviews were VERY relaxed. Everyone's interviews were done at 2:30, and the last 30 minutes was a quick talk by the chair of the admissions committee (I left early to catch the shuttle, so if you're worried about transportation issues, just let the staff know).
For those of you that have interviewed, they shared some info that might be of use to you. They've sent out ~15 acceptances thus far; decisions go out biweekly, but the committee meets to review and rank people weekly. If you've interviewed and haven't been ranked, it's more than likely due to one of your interviewers being absent at the committee meeting. They won't discuss/rank you if one of your interviewers is absent. As far as the rest of the season goes, they're planning on sending out ~50 acceptances by the start of the new year. After that, all acceptances will be to replace those that withdraw (i.e., when one person withdraws, another acceptance will go out to replace that person). Marcy said they expect to send out ~75 acceptances total from the ~300 people that interview. As far as other numbers go, they received ~4200 applications and requested LORs from ~1600 applicants.
As far as my opinions/suggestions, I would DEFINITELY try and stay a couple of days and hang out with the students if at all possible and explore as much of Rochester as possible. That's really what sold me - Nerday and SortaBigDeal are incredible, so definitely try and meet them if you can (didn't get a chance to meet bamtuba). The insight from students is extremely valuable, and a lot of the stuff I talked about with them wasn't mentioned on the interview day.
Best of luck!