For us, it doesn't save money, but the gap is slowly closing, and the DP will likely come into favor for our next trip. Right now, there isn't a DP that matches our eating habits, and it isn't enough of a bargain for us to change our habits overmuch to accommodate it.
For example, we usually order water with meals, and would rather get our dessert later on, instead of immediately after our meal in most cases. DH needs 3 full meals every day, but we don't eat enough table service to justify the deluxe plan. For our upcoming trip, we only have 3 table service meals planned, and while we COULD add more and do the regular dining plan, we would be spending more than what we would spend on the meals we want to do just for the sake of making the dining plan a good value. The quick service plan is probably the closest to our habits, but we'll still be paying out of pocket for all our table service meals.
I expect that when DD is a bit older, we'll likely have at least one trip when the DP is a better value than paying OOP (those darn princess meals). However, our last trip and our next trip were planned less than 6 months out, so our ability to get into some of the restaurants we would want to do on the dining plan has been limited anyway.
It also helps that we don't particularly like character dining. For our upcoming trip, I have one character meal planned, but to some degree that's because we've been to every other table service meal in that park, so I figured it was as good a time as any to try it while we have kids the age to appreciate it.