We LOVE it. We tried it for free last September (same deal as you have this year) and stuffed ourselves like the true pigs that we are.
All you do is use your room key which acts as your park ticket, credit card and now your dining card. You tell the waiter at the beginning of the meal that you are on the dining plan.
Each person gets 1 snack, 1 fast food meal and 1 sit down meal/night of your stay. The fast food includes a drink and dessert. The sit down includes 1 appetizer, 1 entree and 1 dessert and drinks (nonalcoholic).
We kept moving our PS ressies trying to get hungry again for the next meal. It was insane the amount of food you get. We were using our snacks to buy water!