I'd definitely recommend the dining room at night- the ambience is wonderful and the formal nights are really fun. The attire is very resort casual- besides on formal nights, I even saw shorts and the like in the dining room.
Breakfast is a good time to enjoy the dining room too, just as lunch is typically less crowded in the buffet, especially when you're in port and alot are off the ship. I also liked to order breakfast to the room. I'm usually a cereal/fruit person, so I'd order those items to my room to eat while I got ready for the day.
Majesty OTS, 4/07
Mariner OTS, 4/08
Adventure OTS, 4/09