We just returned and did not use the dining plan although I had initially wanted to (we used an AP rate and therefore weren't eligible). More than once on this trip I realized I was glad we didn't have the dining plan because we wouldn't have gotten our monies worth.
Personally it would have encouraged me to overeat. At our first lunch DH & I were talking about the dining plan. I was full from my meal, but I commented that if I had a dessert coming to me I know I would have eaten it. But that's just my personality, those with more self control probably would do just fine
The other issue is that I would constantly be trying to "get my monies worth, " ordering the appetizer, entree and dessert and eating all or most of it even if I was already full. Again, that's just me -I also have a thing about wasting food and that too would encourage me to finish everything. I just hate doing that and don't like leaving things on my plate; thinking about food getting thrown away bothers me.
Also, and this circumstance wouldn't apply to everyone obviously, but we had an infant with us and sitting down to one meal a day just wasn't in the cards.
I think it's a good deal for those who want a sit down meal each day and if you space out your meals and don't overindulge it can work.