We had the ADDP. Not everyone needs to get the plan. You can actually purchase the plan when you check out at the participating restaurants. They put a wristband on you wrist for the day.
You get a lot of food with the plan. 1 main meal, 1 side and a drink. The side could be a salad, French fries, fresh fruit (grapes, strawberries), cake and cookies (DS13 loved the cookies.) The main meal could already include the french fries, so you would still get to pick a side. The restaurants are actually spread out enough that when you get thirsty or need a snack, there would be a semi-close restaurant. We loved the Seafire (fajitas were yummy and so were the chicken tenders!) and Spice Mill (burgers, chicken sandwiches) and hated the Smokehouse. There's also a pizza place and a few others around the park. You get a lot with your meal and might not want too many snacks.
Depending on how long the parks were open, I would definitely consider getting it again. We had a late lunch, dinner, and a late dinner before we left. 3 meals for $34.99 plus several hot chocolates. Nice!
I did a trip report on the Universal TR forum with some food pictures. It starts "I Won a Trip to Sea World !?! ....)