Their "official" stance is that acceptance letters will be sent out in January. However, they do give the impression that some people will hear back rather quickly, which is obviously the case. On the first day of your interview session you will meet with some current students. The students I met with basically said the same thing, that some of their classmates heard back really soon, while others didn't get accepted until January. So while some may get accepted sooner than others, not hearing back from them right away doesn't mean you weren't accepted!
As far as the actual interviewing goes, that is all on the second day. The first day you sit in on a pharmacology class (which is awesome, by the way), and then meet with some of the program directors to discuss the program and financial aid, etc. You then split into smaller groups and meet with some current students. After lunch comes essay writing and an aptitude test.
I believe the interviews are scheduled from 8-12, but I was out of there before 10am. Like I said before, the interviews are really laid back and more of a conversation than anything. They already know how smart everyone there is and what they've accomplished, now they just want to see what everyone is like as a person. So I really suggest just relaxing and being yourself, rather than worrying about coming up with a perfect answer to any questions they might ask you.