i feel that i should add something from another perspective to the op's question.
I went to a guaranteed med program myself and I thought it was one of the best decisions i ever made. As far as the "being completely committed from day one" argument goes, I never felt that I was completely overwhelmed by my curriculum at any point. In fact, I had a lot of time in my schedule to take elective classes and even pursue a minor. The main thing you want to find out is whether you can apply out of this GW program if possible. You do not want to get locked into one medical school this early in the game. Personally, my program let me apply out and admission to my guaranteed med school did not require me to take the MCAT. So it was a win-win situation. I suggest you find out some of the requirements to the program that you have been accepted to. I know many people (friends, cousins, acquaintances) that would have killed to be in my position of having an acceptance because when the application cycle started they had to deal with a lot of stress and uncertainty about their future careers. Obviously, if you are confident in yourself and are able to do well in college then you can practically get into any med school from any undergrad college in the country. From personal experience, however, I would say that it is nice to have a guarantee.
If you are curious at all, I decided to take the MCAT and decided to apply out and starting this fall i will be starting at a medical school other than the one that I had a guaranteed spot in.
So once again, it all depends on how confident you are of doing well in NYU with no guarantee, on the program requirements (ability to apply out etc.), and on how confident you are about pursuing medicine as your career.
Hope this helps.
If you have any other questions feel free to PM me. Good Luck.