We are considering adding
DDP to our trip in June (four nights) and have been crunching the numbers. Whether or not it makes sense really depends on what table service meals you plan to eat. The DDP is $45.99 per day. If you use it for Crystal Palace Breakfast ($23), counter service meal, and a bottle of water, you will lose money on the plan. If you eat dinner at Chefs de France and get the Filet ($35), Creme Brulee ($7), and a Coke ($3), plus a counter service meal and snack, you'll be ahead on the plan for that day.
If you know where you will want to eat, check their menus and prices, and you can figure out if the plan works for you.