We have done both the Superstar Breakfast at Cafe LaBamba in Universal Studios and the Grinch breakfast during Grinchmas at IofA. Both were tremendous. The food is standard fare, but the character interaction was incredible. Gru was just awesome, the Minion with the bananas was hysterical, and EB from Hop teaching my son to drum on the table with his drumsticks is one of those timeless memories for us. We always booked for the earliest time. On one occasion, we were the only people walking the road past T2 and the Horror Makeup show, and it was a super cool, eerie feeling. My wife also thinks it gets us the freshest food, not sure if that is true, but it seems logical.
Others have discussed character meals at the hotels, but we have not experienced those as of yet.