While we always have dinner in the MDR, we alternate breakfast/lunch between buffet and MDR, depending on how the mood strikes us that day. When I have a good breakfast I usually just have a salad for lunch to save room for dinner.
On Carnival, a menu is posted outside the dining room for the breakfast, lunch and dinner menu of the day so you can always run up and see ahead of time what they are having for lunch and dinner. Breakfast fare is the same each day.
Been there - done that:
2005 Holiday, Sensation, Conquest,
2006 Conquest, Celebration, Holiday,
2007 Freedom Grand Med, Holiday
2008 Fantasy & Sensation,
2009 Fantasy, Holiday & Dream Grand Med
2010 Fantasy and B2B Elation
2011 Monarch of the Seas
2012 Booked - Breeze from Barcelona 12 days