I have gone here so many times over the years, for breakfast, lunch, and dinner, in fact! It's really terrific! I enjoy all the food here tremendously. It's also a beautiful location and quite spacious. It's always lovely to eat here. I think it's probably the best overall choice to eat in Magic Kingdom, actually, certainly the most affordable and most bang for your buck of the sit-down restaurants, Skipper Canteen sight unseen.
I think there are always plenty of choices of food to eat at too, and something for everyone. It's certainly miles better than, say, the buffet at Chef Mickey's which is probably the worst buffet in the entire of Disney World. I have better memories of Crystal Palace than the other character dining buffets I've been to as well, and I've been to all of them save whatever they have at Swan/Dolphin.
As for characters, it's all the Winnie the Pooh ones, which include him, and Piglet, and Eoyre, and Tigger, too! The character interactions are some of the best and longest at the parks, to be honest, and they're pretty nice with always having helpers available to take pictures of your group if you need it, too. They also have a cute musical conga like parade for the little ones, where they can join the characters during the meal and march through the palace.
It's a great experience, I couldn't recommend it higher. I can't quite remember the exact dishes but there's lots to pick from, from pasta to carving board stations for meat. I am always stuffed. I wouldn't think anyone, even picky eaters, would have a problem here. It's not quite fine dining, but it's very, very good and tasty and I feel compares favorably to all the other character buffets. Sometimes the listed menus online don't tell the whole story and aren't completely accurate.
If you really want a buffet that isn't generic at all, than I'd suggest going to Boma at Animal Kingdom Lodge's Jambo House, if you desire more exciting and adventurous offerings that are delicious.