Crystal Palace (in MK): Best to get a pre-park opening breakfast! You get into the park early, get some great castle pics, head into the restaurant. Winnie the Pooh gang is awesome, the ambiance of the place is pretty awesome, and the food is great, including build your own omelet's and such. Definitely go before the park opens
Cinderella's Royal Table: I *personally* wouldn't say it's worth it for breakfast, but it is awesome to eat in the castle and with princesses. Haven't done breakfast here yet, but don't think the food is worth the price, would do dinner instead.Go before the park opens
Tusker House (ak) Another great food place, you can get different, African inspired dishes versus just the standard American fare, Mickey & the gang come to say hello, and service is usually good. I'd say go before the park is open, or around 10am.
Those are definitely my favorites, and I do highly recommend Crystal Palace!