MGM - Only place that serves a 'proper' breakfast is ABC but we prefer to wait till 11.30am for the salmon and cream cheese bagels at Starring Rolls (to die for!)
AK - Definitley Tusker House
Epcot - We have eaten at the food court near the Living with the Land (with the balloons) - although not really fond of this eaterie.
MK - We have never eaten CS at MK - usually go for a character meal or if not, usually so busy don't think about food till 11.00/11.30 when we head to Columbia Harbor House
Hope this helps a little.