Just my two cents, but we have dined at a lot of Disney restaurants over the last 20+ years. We don't use the dining plan. We use a program that has had many names, I think. Right now it is call "Tables in Wonderland". I believe you have to be a FL resident or an annual passholder to buy the membership. For $40 or $50 (or so?) you buy a membership. You get 20% off on food and beverage for up to 10 diners at almost every sit down restaurant at WDW.
We are major food snobs, and we find some really great dining at WDW. The mediocre to poor dining at WDW is expensive anyway, so why not splurge once a day and eat your other inexpensively or in your DVC home? I think you can make that work even if you are on the dining plan, but I have never tried.
Here are the restaurants that have been consistently good:
Brown Derby (lunch, dinner, anytime - love this one)
Coral Reef (we only go for lunch, and it's a nice break)
Jiko and Boma (even though Boma is a buffet, I recommend it)
California Grill (time it so fireworks are during dessert)
Flying Fish (Boardwalk)
Yachtsman (I think that's the name. In Yacht Club - steakhouse)
Crystal Palace, surprisingly good food, and I detest buffets.The dessert party at MK during fireworks - whatever that is called.
Wolfgang Pucks at Downtown Disney - great sushi and pizza (odd combo)
La Hacienda de San Angel - gotta disagree with those who compare it with Chili's. I would never, ever, even in the airport, even if stranded, ever eat at Chili's. I did that one time. Never again. La Hacienda has a more authentic Mexican menu. Maybe does not agree with those looking for Tex Mex. It's really good food, though. The waitstaff was wonderful, and the margaritas, though expensive and a little sweet for my taste, were a big hit at my Mom's 75th birthday party, and are definitely the best at Disney.
My family likes some of the restaurants in Swan and Dolphin, Garden Grove and one other, but I can't remember the name. I think they are mediocre, expensive and not even Disney experiences. Only exception is Tod English place - BlueZoo, I think is the name. It's really good, but not Disney (which can be good for a break!)
For the fun but not necessarily for the food - but uses up some of that Dining Plan - 50s PrimeTime Cafe and Sci-Fi Dine In theatre in Hollywood Studios.
Ice Cream - Ghiradelli's (or however you spell that!) in Downtown Disney on the Marketplace end - good break while doing your shopping for gifts to take back home.
Also for ice cream - Beaches and Cream. Their food is pretty good, too. Can be a really long wait.
And one more ice cream: Seashore Sweets has good ice cream cones when you are walking around the Boardwalk. Their candy is ridiculously expensive, as is candy at Disney in general. I don't think you can use the meal plan for candy as a snack, can you?
Boardwalk Bakery. Everything is baked there. I do my best to stay away from here. It all looks really good when I go in to get my coffee. I know that the apple turnovers are good. Can't speak for the rest, but it looks good.
Pastries from France in Epcot.
Rose and Crown for a beer and to watch Illuminations, though you will probably have to eat dinner to get to see the fireworks. I am not a fish and chips fan, but my husband says it is good.
Character ice cream party at the restaurant at "The Land" in Epcot. Don't know if that still exists, but my kids used to love that when they were the right ages.
Two important and delicious words on a hot day in the MK - Dole Whip. 'Nuff said. (MK near Adventure Land entrance)
I won't include a list of places to avoid at all costs, even though I think there are a few. If I write that down, I am sure to insult someone else's favorite place. I have never had any food as bad as the food I once had at Chili's anywhere at Disney.
Happy dining!