Personally, we haven't done it yet but we decided to do it based on ALOT of reading of opinions. We've got the deluxe plan booked for Sept.
The big reason we're doing it is so that we can do alot of character meals....we're bringing our DD4. So I really want her to have alot of fun. Also, we're going to Cinderella's castle for a breakfast and a dinner and also Narcoosees. ( all 2 credit). But I kind of figured out the pricing of each of the restaurants we picked, plus snacks, plus the refillable cup and we'll wind up saving about $ 500.
I also like the fact that we don't have to think about what we want to order....it's paid for. ( except tips) So that's nice.
Alot of people will say it's too much food and you spend too much valuable park time. I think it depends on your particular family. I look at it as a nice break to sit, talk and relax. My DD is 4.... I don't want her so overwhelmed that she doesn't have fun. She's good when she can sit and relax for a minute. We're big fans of "sit down meals" at home, so for us it's normal. We don't eat big, but we do sit down together to connect with each other. So I don't look at it as wasting park time. Also, while it IS alot of food, it's your choice HOW MUCH you eat. You don't have to order dessert.... you can order salads, fruit... or at the buffet, eat light.
Really, I love it for the experiences of going to all the character meals and the 2 credit meals. I don't want to deal w/ counter service or "eating on the go".
Have fun planning your vacation !!

(sorry for this being so long!!)