Usually they have certain requirements that you have to fulfill (like get a 26 on MCAT and maintain a 3.5 GPA). So if you are happy with the school and have met their requirements I say save your money and don't apply anywhere else
I'm no expert, but I have looked at the requirements of a few assured acceptance programs, and I believe that one of the stipulations for all of them was that you do not apply to any other schools. Of course you have to meet other GPA requirements as well. The upside is skipping the glide year. The down side is that if you don't make the cut, you may wind up adding another year of application time.