I think there are 2 general ways to approach this: "test driving" and "essentially-interviewing".
Test driving - when you aren't certain of the type of program you like (size, location, private vs. university, specialty, etc.) and so you span a couple of options.
Essentially-interviewing - when you're basically auditioning for a month in the hopes they'll like you
Having gone through the process and now seeing from the closed-door resident match meetings, it's hard to give a recommendation. From the standpoint of programs at which you rotate, they judge you on that month... just understand that they'll remember the one time you slacked much more clearly than the other 27.99 days you worked your a$$ off. I remember the story of a student who was doing well until he and his resident got an ER consult for compartment syndrome and the student asked if they could get some lunch first. Perhaps reasonable, but he got the axe for that one comment.
On the other hand, think of it this way: many folks match at places where they didn't rotate. I applied to 50 programs and only had face-time at 4 (including my home program). I matched my first choice to a program I'd never seen before my interview. I'd like to think that my honestly saying that I liked the program BECAUSE of size, location, type, etc. may've helped them believe I was serious and not just kissing up like everyone does. No matter where you go for interviews, you'll be asked where you rotated and what you liked/disliked about the place, and it's good to have an honest answer. I was lucky my program took me sight unseen, and I've been very happy since.
So, if there's one or two places that you REALLY see yourself at, rotate there, bust your tail, and don't EVER offend/slack. Otherwise, if you don't know, pick some different types and test-drive. Just my 2 cents.
