We did the Deluxe plan when we went this past June and did nothing but table service, character meals and dinner shows. The food was pretty good overall and we kept track of all the meal costs and the dining plan saved us about $400 over paying cash. The refillable mug was nice but we only used it twice since we ate most meals away from the resort.
However, it did take a lot of advanced planning to squeeze in all those reservations and keep on top of them while we were there. I felt like we were doing nothing but killing time between meals. We made maximum use of all the meal credits, but did end up with 18 unused snack credits at the end of our stay (2 per day per person is a lot on top of the other credits), which we did use by buying up a bunch of stuff the last day for the drive home.
You will save money with the Deluxe plan but to get the most benefit from it (and the biggest cost savings) you have to plan nothing but table service, character meals and dinner shows. Using it on a counter service meal is a waste in my opinion.
We have done the dining plan in one form or another the last 4 trips we have made. We are going back again in October and I'm going to go "old school" and try eating a little in the room and pay cash for the rest and see how we come out. I want this trip to be about the other stuff, not just about the food. Being on the dining plan always made me feel like we were obligated to use every credit, often times when we weren't even hungry, just to get my money's worth.
It isn't a bad thing, it just requires a lot of planning to get your money's worth. This planning and keeping on top of all the reservations can sometimes come at the expense of the leisurely vacation you came to Disney for in the first place.