Normally when we visit for 3 days, we get it two of those days. Its great if you have big eaters in the family. A typical meal at one of the six places that the meal deal is accepted can cost between 7-9 dollars. Toss in the sweet that you get (normally a cookie or some sort of lemon cake) and you will be at 9-11 dollars. So, if you eat two meals you are about breaking even (maybe even losing money). However, when we do the meal deal, we eat one meal right away as sort of a "breakfast" and then around 2 we eat lunch, and then about an hour before park closes we eat dinner.
They stop serving food at the places 30 minutes before the park closes, so make sure to get everything before then. Also, last time we discovered that you did not have to get the meal to get the cookie! So, we went and each got two cookies before we left. Had one as a late night snack and one in the morning before the plane ride home.
So, basically if your family can eat 3 times in the parks, it is really worth it. If not, I would skip it. Also, DO NOT get the drink cup!!! You can buy a cup at the parks that costs about $7.00 but you get $.79 refills FOR LIFE! The Meal Deal cup you get can only be refilled for free when you have the meal deal. It is really not worth it to get the meal deal cup, but the only one will save you a ton!