First, congratulations!! That is really exciting. Getting into one program is always good, but having the pick of the litter is even better! I don't know much about the Duke program since it's relatively new but....
I'm a current student at Boston University in their MAMS program, and I have to say it has been the best decision for me. The faculty are supportive and are extremely involved in helping you with your medical school applications. They really care about your development as a student and as a person, and I've felt more confident about my decision to pursue a career in medicine after attending their program. I've spoken to some recent grads, and they said the curriculum at Boston is top-notch. The program has courses that are IDENTICAL to their medical school curriculum which is extremely valuable and gives you a leg up on your peers which is very important going into the USMLE I.
Hope this helps. Good luck in your endeavors!