It depends,if I get to the park on a cool day at 11am and the park closes at 6pm,I would obviously pass on the all day dining deal.If you show up close to the opening time during summertime and the park is open until 9 or 10pm then you'll be insane not to get it.
The factors you have to think about are how many meals will you get in considering the time you'll be at the park,if you get there near opening time you'll also be able to have breakfast at the Voyager's smokehouse which I believe is the restaurant that offers breakfast.If you're going during the hotter months having the ability to just go in the restaurants at any time to get a soda or bottle of water is priceless,during the cooler months you will not need to drink as much so it wouldn't be as necessary.Also aside from the meals you can also go in anytime and grab some fruit or a dessert to eat as a snack which is another plus to get it.
The price for the entrees are around $7-$14,depending on what you get which is typical pricing for most theme parks.Desserts are $3-$4 and are very good when compared to counter service desserts at the other area parks as they're made in house.Drinks will be around $3 so you have to figure on close to $15 per person if you get an entree,dessert and drink,so as long as you eat twice you're at least close to breaking even.If you have light eaters the plan might not work as well for them.