2 years ago we did the basic DDP. It fit very well into our eating plans at the time, and we were doing all-you-can-eat dinners so I knew what it would have cost for those OOP. We were going to do the basic DDP again last month, but then things changed.
Last month I upgraded my ticket to an AP. The difference in cost was $165 including tax (we get a $100 DVC member discount on APs). Then, I spent $75 on the TiW card.
We went for 10 nights, DH, me and our 2 boys (ages 3 and 5). If we were on the basic DDP, it would not have fit in with our restaurant plans for this trip. We had too many TS for it, but too few CS and would have had tons of CS credits leftover. We had 18 TS restaurants, which would have been 19 credits on the deluxe plan since one of them was CRT (the rest were 1-TS restaurants). We had 2 CS meals, plus 1 meal at Picabu at the Dolphin, but they don't take the dining plan so we would not have been able to use a credit for it. The kids got lunch at a CS at MK one day, but DH and I were still too full from breakfast at Crystal Palace so we only snacked. Throughout the whole 10-night trip, we bought 24 items that would have been considered snack credits on the DDP.
So.....overall, if we were on the deluxe dining plan, we would have used 21 meal credits, 24 snack credits, paid OOP for lunch at Picabu in the Dolphin, plus the kids each would have used another credit for lunch at MK, and we would have paid full price for the alcohol DH and I sometimes enjoyed at dinner. We would have been allotted a total of 30 meals each, 80 snack credits altogether

!
Therefore, we would have had 9 adult meal credits left per adult, 8 child meal credits left per child, and 56 snacks altogether at the end of our trip! As far as costs are concerned, the price of upgrading my ticket to an AP, PLUS buying the TiW card, PLUS the cost of food (not counting alcohol or tips, but counting tax) was just over $1600. The deluxe dining plan would have cost us $1859 for the 10 nights for the 4 of us. In addition, we never ordered an app AND a dessert EACH at TS restaurants. We didn't get dessert at either CS lunch either. We sometimes just split an app and a dessert between the 2 of us. Sometimes we were too full for dessert, but we love our sweets, so later on we would get something from Boardwalk Bakery or somewhere in the theme park we were in. One time, I got an app as my entree at lunch. We liked not worrying about whether or not our meal components would be covered by the dining plan, and what is or isn't considered a snack credit.
Something else that you should know (I didn't know this before my trip)...our server at Kouzzina informed us that although on the kids' menu, it states the full price of the 3-course meals for children that are listed on their menu, you could just get the entree for them and not the app (my kids didn't want the app most of the time), and you just pay for the entree. There is a certain amount allotted for each course of the children's menu, and you pay for each one. All three courses add up to the amount listed on the children's menu. Many times, my kids just wanted a hamburger with fries, but did not want soup or salad, or ice cream because we went to the Boardwalk Bakery later on to get dessert.
Bottom line, my opinion of the deluxe plan is that it is a great deal if you tend to eat a 3-course meal when you go to a restaurant, if you plan to go to a lot of signature restaurants, or if you would have spent at least that much amount on food when paying OOP (could be hard to figure out what you would order though). Perhaps it would work better for us if we were on a shorter trip, but for a long one, it just would have been too much for us. Others will feel differently and would never go without the deluxe plan. That's why they give us options!