Do you want to eat like you are on a great expensive vacation or do you want to pinch pennies and eat like you are poor?
Vacation won for us, glad it did, it was worth every penny. We would have spent the same or very close to the same if we didn't have the plan and would have eaten terribly.
As far as the flexible part, we had no problem making priority seatings in the morning for a resturant in or near the park we were in that night. So, when we knew we were doing extra evening hours at Epcot, we made a ressie for a resturant in Epcot, Yacht's Club, or Beaches. Easy. If you aren't even sure if you will be in a park that night, than I am sorry, that is TOO disorganized to even be taking a Disney vacation.
Add it, you won't regret it.
Oh, and there is a key code floating around for free dining plan if you stay at a value resort... ask and you may receive...
Nora