We do not use the dining plan. It is not cost-effective for the way that we like to dine. It is true that we could purchase the dining plan, and we could make it work in a cost-effective manner --- but we would have to adjust our preferences.
We are a family of 3 adults (me, DH, and DS 22).
We typically do at least one TS each day. Some of our favorite TS restaurants are signature (2 credits), which are not a good value on the dining plan. We do not often order dessert -- maybe once or twice during the week -- and, even then, we will share. Occasionally, we will want to share an appetizer. Sometimes, if we're not really hungry, we might want to simply order an appetizer and a salad. We also have a couple of favorite non-dining-plan restaurants where, of course, we must pay OOP.
We do usually do a CS each day --- but even then, we don't always want one CS per person. Some of the CS meals are large enough for 2 of us to share. And we never have dessert with lunch.
I understand that some people like the dining plan as a budgeting tool; i.e., they know exactly what they will be spending on food. That doesn't matter to us. We've been to Disney enough times so that we have a pretty good idea of what our food budget should be.
So, for a variety of reasons, it's not cost effective for us, and it doesn't offer us the flexibility of dining where we want to dine --- maybe off-property, maybe an additional CS, maybe an appetizer and a salad as a meal.
We simply charge everything on our KTTW card or, if off-property, OOP on a credit card.