hi there- first of all, congratulations on your interview! i'm a current 2nd-year student in the JMP who spends way too much time on the internet and finds myself on SDN every so often
the interviews are really chill- everyone usually has 2, with JMP faculty, associated faculty, or students on the adcom. we are a pretty small program (12 students per class) and you are the first interview i've heard of so far, which is great there are ~60 interviews/year for the 12 slots out of (if i remember correctly) ~300 applications. let me know if you have any questions, and i'll be sure to check in more often.