I think it totally depends on your habits ...
I think $$-wise, it's well worth it considering the cost of the DDP is equivilent to just one sit down dinner so the Counter Service and Snack credits are 'free'. And I think if you want to eat all that food, you get more than your money's worth.
However, for us, it's not worth it. When we go to The World, we don't usually have a TS every day. We snack and eat lighter and hate having to deal with the schedules of reservations and all that jazz. On a 5-Night trip, we might have 1-2 TS meals. Sure, we could make it worth it by eating more TS, but then we're spending a lot more money to save a little money since we normally wouldn't do TS anyways -- if that makes sense?
Now, my uncle has DVC and they do DDP *all the time* and for them it's a huge savings because they have at least 1 TS per day anyways -- usually a dinner.
The way I think about the value of DDP is like this:
If you normally eat at least (1) TS meal per day, then get the DDP. You'll find yourself completely stuffed and trying food that you might have never opted for (NY Strip vs. Chicken Breast, etc) and maybe trying that extra appetizer as well.
It has *nothing* to do with the quantity of food. As apparent on this thread, I think everyone agrees that you don't go hungry on the DDP. The question is, would you normally eat all that food anyways?