In 2009, 2010, 2011, 2012, and 2013 my wife and I bought DxDP and saved, on average, between 15% and 30%.
In February 2014, we did out of pocket. We saved 25% by NOT buying the DxDP. In fact, our out of pocket expenses were very much in line with what one would pay if they bought the DDP and bought appetizers for the sit down meals. But, we did NO counter service at all. Every meal we ate was a sit down table service meal. During this trip, we ate at Narcoossee's (twice), Hollywood Brown Derby, Artist Point, Citricos, California Grill, 'Ohana, Cape May Cafe, Kona (twice), Liberty Tree Tavern, Grand Floridian Cafe, Bongos, San Angel Inn, Via Napoli, Yak and Yeti, and Hollywood and Vine. We didn't skimp on anything. We had the whole Maine Lobster at Narcoossee's, Filets everywhere, Buffalo, surf and turf, ice cream and funnel cake as snacks, and had appetizers and dessert with virtually every meal. So, how did we eat like Kings for just a little more than the price of DDP? It's actually very easy. Disney's plan savings assumes you're going to eat all those snacks. We typically were taking those snacks home, eating only a few in the park. Disney's plan savings on DxDP also assumes every person is going to order the most expensive appetizer, entree, and dessert on the menu. While we didn't scrimp at all, there were some meals where we didn't want the dessert (HBD's three tiny samplers, for example), or didn't think we were hungry enough to have an appetizer, entree, and dessert. We didn't take any snacks home, because they weren't "included" in out out of pocket dining plan.
My wife and I were a little apprehensive about spending more than the DxDP would have cost, until we got out receipts from some of the earlier years and added up the costs. In earlier years, we saved less than 5% when snacks were not factored in. When we subtracted apps and desserts we wouldn't have ordered but for the fact that they were included, the "savings" completely disappeared. So, we went into our trip and didn't think about what stuff costs. We chose what we wanted to eat, and where we wanted to eat, and only figured out the total cost after we got home.