i went to williams (grrrr.) and had a few friends who applied and got accepted to this program sophomore year. i think that it is a great program b/c it allows you to explore and learn so much more in undergrad, rather than concentrating on your premed courses...at a place like amherst (a small college), it is hard to justify sitting in a classroom with 100 students...it always was for me...i much preferred my 15 student history classes...
my advice - if you know for sure that you want to go to med school, apply!!! and become a history major : )