I have to preface by saying that I LIVE for my next Walt Disney World Vacation - That being said, I literally survey my husband and kids on what they'd want off each menu for each restaurant for every day of our vacation. I get the subtotal and add in the tax & tip. I also do this taking all discounts into consideration: TIW discount, AP discount, DVC discount. Then I come up with a comparision that I can judge which path is best.

Now, you have to be careful because sometimes you will order more food on the Dining Plan than you normally would - which means and increased TIP! I also average in what I think our rough snack costs will be and the every so cool refillable resort mugs.
I do this for every trip because I keep thinking that the dining plan might be worth it. For the most part, we end up saving more using TIW (old DDE). But again, we are Table Service kind of people. I think the dining plan might be a great deal for someone who eats counter service at least once a day. I've even tried comparing costs with the Deluxe Dining Plan as a possiblity - still no savings for us.
We did try the dining plan last year. One of daughters was only able to stay with us for half the trip. So we were able to use her portion after she left. That's the only reason why it ended up being a savings. We ate WAY MORE than we should of. But last year, you received an appetizer, entree and desert. Now, it seems you only get the entree and dessert which I would think would even lower your savings more. We usually get one appetizer for our whole family to share and maybe one or two desserts at most, so TIW is our best bet.
Good Luck no matter what you choose.
