I love the Leaky Cauldron and Three Broomsticks. They both have a fairly unique menu for theme parks (British pub food) and I always find the food to be really good. The theming is also incredible! I think it's worth the wait every time. The menus are slightly different, but I wouldn't necessarily feel the need to eat at both of them, especially if you are only visiting for one or two days.
As a note, I went to Universal Studios Hollywood and found that they have a vegetarian platter at Three Broomsticks. It's basically all the veggies from the other dishes (sautéed cabbage, grilled tomatoes, peas, mashed potatoes) plus grilled asparagus. I don't think I've seen it on the menu at Orlando, which is a shame because it really was delicious, and I'm not even a vegetarian!
Not really a must eat, but I love the food court in The Simpsons area. There are a lot of fun Simpsons jokes, and one area is themed like the inside of Moe's Tavern, which is cool to sit inside. There is a Lisa themed section that has vegetarian and healthy items grab-and-go style and I remember having a few good salads over there. Even if you're not a Simpsons fan, they have a lot of different counters to order from, which is great if your are with a group of people who all want something different.