Yes, the Plaza is indeed a great deal if you're not on the dining plan, and my family enjoys it.
Another tip: if you schedule TS lunches instead of dinners, that can also shave a lot of money off your bill (for example, lunch at the Biergarten -- which I'd highly recommend -- costs a third less than dinner, even though the lunch and dinner buffets have virtually all of the same items, and an a la carte lunch entree and drink at Liberty Tree Tavern, another tasty place, will cost you no more than $20, compared with $32 for the all-you-can-eat dinner. You'll also spend 30-50% less on Be Our Guest when it's serving counter service lunch instead of table service dinner, even though the setting is the same and servers will deliver your meal to the table either way).
Note: some restaurants however, such as Sci-Fi and 50's PrimeTime in Hollywood Studios, have "all day" menus that give you the same food for the same price no matter which meal you schedule, and are thus among the cheaper TS options if you want your TS meals to be dinners instead of lunches. If that's your preference, you may want to seek out those types of places.
And if you're going to Downtown Disney, I second the Raglan Road recommendation. It's not necessarily the cheapest if you want things like steak and/or seafood, but the quality is well worth the price point, and would be even if it was located far outside of Disney World (something that can't be said for many Disney restaurants).
