I withdrew my application when they offerred me an interview, but my roommate went to his interview, and here is what tidbits I do know.
1) He didn't stay with a student (he never plans ahead for interview trips unless flights are required). However, I've stayed with students at other schools and have found it really valuable. I suggest you do it.
2) There are two interviews. One with an adcom member and and a second with a faculty member. All they know is your name (and you have to tell them your name). (as closed file as it gets). Typically the faculty interview is less stressful than the adcom one, but my roommate got drilled during his faculty interview, so be ready for anything. My roommate has been to 7 interviews, and he said this was the most stressful by far.
3) Your day is done around 4. You have one interview in the morning and the other in the afternoon. The last interviews start at 3pm (although most interview at 2pm).
That's about all I know. Good luck.