I didn't defer a year, but I did the post-bac program last year.
If you're already in med school, I wouldn't defer a year to do the NIH pre-IRTA program. Half the point of the program is to help you get into medical school. Though I learned a lot of cool stuff and had an awesome experience, I have friends who had a terrible time. It all depends which of the institutes you get accepted to work at and if you are in their clinical section or in one of the many labs.