I just returned from 5 days at Disney (with a quick side trip to Universal) and wanted to share my experiences.
First things first, I'm gluten free, and Disney consistently bends over backwards for diners with food allergies/intolerances. I've been gluten free for 7 years, so I have this more or less down to a science, and I was incredibly impressed with both my options at the Disney parks and hotels, and how knowledgeable the staff were.
In terms of the food...
Breakfasts: We did a character breakfast at 1900 Park Faire at the Grand Floridian the first day. The chef made me gluten free Mickey waffles (!), which was very exciting, and the rest of the food off the buffet was just OK.
The other three days, we had breakfast at Boma, the buffet restaurant at the Animal Kingdom Lodge, where we were staying. Buffets tend to make me very apprehensive, as the risk of cross-contamination is so high, and the food is usually not the best, but we were very impressed with Boma, so much that we had breakfast there the next two days as well. The food was fresh and well-made, and Chris, the chef, was wonderful. He walked me around the buffet the first day and showed me exactly what I could and couldn't have, and also had plenty of GF treats (doughnuts! muffins!) and yes, Mickey waffles, available for GF guests as well.
Lunches were mostly eaten in the parks. Most of the quick-service restaurants (the counter-service ones) have GF options on hand like GF rolls, GF pizza, etc. Flame Tree BBQ in Animal Kingdom was probably the best - the pork sandwich was delicious, and Liberty Tavern in the America pavilion at Epcot was solid as well. We also had two lunches at Mara, the quick-service restaurant at the Animal Kingdom Lodge, and we felt that the food was well-prepared there as well, although the service was a bit slow.
Marrakech (Morocco Pavilion at Epcot): We find that the restaurants in the parks are usually not as great as the restaurants at the resorts, so while Marrakech is definitely a solid in-park choice, it wasn't our favorite meal of the trip.
Sanaa (Animal Kingdom Lodge): We had been very curious about Jiko: The Cooking Place, but as we were using the Disney Dining Plan on this trip, we opted for Sanaa as it only used one dinner voucher per person instead of two, and we were so glad we did. The food was excellent. My mom had the tandoori chicken and I had the curry shrimp and butter chicken combo, and both were great. They also had GF pappadums to go with the dips offered with the bread service. This was probably the best meal of our trip.
Raglan Road (Downtown Disney): I was really excited for Raglan Road after reading how great it was for GF diners on several GF dining/travel blogs, and I just...wasn't impressed. It was probably our best bet in Downtown Disney (at least for GF options) but after waiting 45 minutes, I was expecting an incredible meal and the restaurant just didn't deliver. My risotto was meh and my mom found her fish and chips to be greasy. I wouldn't return here.
Tangerine Cafe (Morocco Pavilion at Epcot): We opted for a quick(-service) dinner at Epcot before the Illuminations show, after having spent the day at Universal Studios. We liked Marrakech, so we figured this was a good bet. The chicken shwarma was the only GF option, and I thought it was pretty tasty, and reasonably authentic. (I ate my fair share of shwarma while in Israel a few years ago.) The hummus was good, although I wish they had GF pita on hand, especially after finding that it was available at Cat Cora's Kouzzina the next night.
Kouzzina (Boardwalk): This was probably the second best meal of the trip. They had GF pita bread to go with the dips that were available as an appetizer - and the dips themselves were great - and the fish stew was excellent. Would definitely return here.
Non-Disney meals: We ate at the Three Broomsticks restaurant at The Wizarding World of Harry Potter at Universal (because I'm a big fan of the books and therefore we had to) and while the atmosphere was fun, the food was nothing special, and I thought the turkey legs were much saltier than the ones found at Disney. That being said, if you're going because you're a Harry Potter fan and want to eat at the Three Broomsticks, it's not TOO bad.
Overall, this was a great trip, and some of the restaurants we ate at were great. The Disney Dining Plan was also a pretty good value if you're going to eat on-property a lot.