For my family me, DH, DD's 7 and 13, it was not worth it. I had TS ADRs for everyday and when I really looked at it all over time, I realized
1) We don't eat enough to justify the DDP.
2) We
rarely get dessert and only sometimes a salad or appetizer with a meal since we get too full to eat the entree.
3) I decided too many TS meant too full tummies for rides

,
less time for rides, touring parks, etc. I did come to
see the place-- I can eat quite fancy at home if I wish...
4) DD- 13 will sometimes do 2 appetizers instead of an entree. Can't do that on DDP-- also she would be paying adult price and only eat
some adult meals.
5) Figuring the costs using the menus, including the few extra TS (OOP) we would be doing due to Character Breakfast and TS dinner both in one day due to our grand gathering, I came out so close (overestimating what I feel we will eat) that I will take the risk of NOT doing the DDP.
Most important reason why not was that I would feel obligated to have all the TS because we paid for them and then eat too much food in order to get a good value (not
rip Disney off, but gee, a salad for an entree when I'm on the DDP? Even If I wanted only a salad, it just would feel like a bad financial decision.)
Take a look at the menus and the places you plan to eat/what foods you might order on a normal day and go from there. It really takes a little personal insight into your family more than anything. Now no tip, no appetizer in '08 makes it infinitely easier to decide IMHO.
In the end, I have finalized our park days using various sources of logic, as well as a coin or two, and have removed a few TS from our plans. (Cutting out dinner at a buffet for $28.99/13.99
plus tax and tip for a
grand total of...$126.25 --cough cough-- when my 2 DD's will eat mac and cheese to instead do a good CS at 1/2 the price if not less makes me feel better alll over

I know I could have the DDP pay for that meal, and we would be able to say we got our money's worth, but in a way, I'd still be wasting it since in reality I would never pay cash for that meal.) I think we will do much better this way. We'll see the truth when we are home!