If we had been staying on site I would not have liked them. Why? Because when staying on site, we go back to the room for a swim/nap and then usually go to a different park in the evening. The bounce back tickets don't allow you to do that.
Using the bounce back tickets was, however, cost effective. We had old park hoppers to use up and along with bounce backs for the middle child (that had made it passed three, thus requiring park admission), it worked out very well because we only needed a couple of days and didn't want to buy another park hopper to have to keep track of until we went on another trip. (Which as it turned out, we bought APs for anyway.)
The bounce back tickets are great if: you don't want/need to park hop and only want a limited number of days as not to have leftovers that must be saved.
Good luck!
Lori