Thanks first of all for the kind words guys. To respond to DS it is' request, let me say that it was by far the EASIEST interview I've ever had (and I've had some easy ones in the past).
At least for me, my interviewer said that she, "just wanted to make sure I didn't have any psychopathic tendencies and that I could speak English well," because I had a strong academic record (and I'm NOT exaggerating here). I have the general impression that unless you really MEAN to screw up, there's pretty much no way you can't do well.
As for the second interview, it just consists of you walking around with a dental student and talking about various things (I didn't even know this was an interview as we started to talk about the Clippers and other random topics). The only annoying thing about the interview is that you spend the first 30 minutes writing an essay but, even then, I don't think that it's really a big deal (just another chance for them to make sure you're literate).
The whole process only lasts about 5 hours (mine went from 10 am to 3 pm) and is very relaxed (even disorganized by some measures). The only thing that pissed me off is that those cheapskates didn't offer us lunch (yes I know, pretty superficial but I was hoping for a free lunch), only giving us a bottle of water and Kudos granola bar.
So yeah, I hope this helps, and if you or anybody else has more specific questions, feel free to PM me. Good luck in your interviews, and, seriously, DON'T worry about it. I can pretty much guarantee that ANY of your other interviews will be harder.