I feel that as long as the DDP does not cost us more than it would have out of pocket, we are getting a great deal. This is because we prefer to pre-pay for dining if we can on vacation, so we know what we are spending before taking the trip. It just helps us budget.
That said, I still looked at restaurant prices before booking the DDP for last summer's trip, because I had not had any experience with it yet and wanted to see if it was worth the money and make sure it did not cost more than paying OOP. I looked at all the TS restaurants we wanted to eat in, several of which were character dinners, and we came out ahead, especially for the kids. DS1 was not on the plan because he is under 3 but kids under 3 eat free at AYCE meals (he would have been able to eat from our food at am a la carte place also, and we had no problem sharing with him at CS lunches either...lots of food!). Our older one was 3, and was $10 a day on the 2008 plan, yet those character dinners would have cost us $13 or so OOP, plus tax (tax is included already in the DDP). For DH and myself, the AYCE dinners were around $25 a person plus tax, and we paid $38 a day per adult. Factoring in the cost of our CS meals (even if we would not have gotten dessert), we came our ahead. Then factoring in the snacks, we really came out ahead.
I did a little research for a la carte places like Spoodles, and other we will be trying on our next trip, and we will still come out ahead even if we get the cheapest item on the menu. I added everything up with the cheapest item because who knows if we will be in the mood for the most expensive thing? Maybe I will want to have a lighter dinner one night and opt for a vegetarian entree, which tends to be lowest in price. So that is what I factored in. I am realistic and I know I am not ordering prime rib or NY Strip EVERY single dinner! Even factoring in the cheaper CS options at CS places we would like to go to, we will still come out ahead. I still think the character dinners are what do it for us, especially for the kids.
For places that are 2TS, it depends how you feel. Are they more worth it on the deluxe plan? Of course...app is included on deluxe. However, it costs a lot more per day for deluxe and it adds up, whereas you can always pay OOP for an appetizer and it would cost you around $16 OOP for the more expensive option, not $30 more per person per day! The dinner shows seem like a great deal for 2 TS credits as well...they include beer and wine and all you can eat plus entertainment!