Jiko...its signature, its really good and overall, not nearly as busy/crowded as some of the other signature resort restaurants.
I'd love to know what time of year you had that experience at Jiko.
We've dined there in May and in October and it's always been busy - no ADR, no table. And even with an ADR there's been a wait to be seated rivaled only by the wait time at CA Grill. It's definitely one of the best signature restaurants on property, so I heartily endorse it, but I don't think Jiko qualifies as a
hidden gem.
Bistro Paris is a hidden gem - they're not on the dining plan so I'm sure that's got something to do with it. A truly memorable, delicious, romantic evening is what we had there - very quiet and subdued atmosphere, especially for a restaurant in the middle of a theme park.
The Grand Floridian Cafe is exceptional for breakfast (that's the only meal we've had there) but I've also heard that lunch and dinner there are quite good.
Raglan Road at Downtown Disney is terrific, especially if you go later in the evening while the Irish band is playing. They have very tasty pub-style food and their bread pudding is wonderful.
Kimono's Sushi Bar at the Swan serves some of the best sushi we've ever had ... if you like sushi. If not, just ignore that.
Bluezoo at the Dolphin is excellent if you like seafood. It can get busy because they get a lot of convention traffic, but they're not on the dining plan so it evens out. A very nice grown-up ambience with wonderful food.