The DDP is a lot of food. I swear American meal portions are bigger than what we normally see in Canada!
The one nice thing is it takes money out of the equation. Since you pay a set price, you don't have to be afraid of ordering an expensive item on the menu.
Here's the thing about the DDP: if I eat wherever and whatever I wish, I come out ahead. Dinner for two under the DDP can often cost around $100 USD. I also get a chance to dine with characters and my meals tend to be at nicer restaurants. However, if I eat normally and economize where opportunities exist (like packing my own snacks), I wouldn't spend as much as what the DDP costs.
Last year, the DDP cost $38/adult. Yes, I can spend that much everyday. However, I can also spend less on my food everyday without much hassle. So really it depends if you want to eat well. If the answer is yes, then you'll easily save money with the DDP as long as you can get reservations at the restaurants you choose. If you want to save some money (like spending it on souvenirs instead), you'll spend less without the DDP.