Eating in the formal dining room for breakfast is a wonderful experience. Unlike one other poster, all my food arrives hot and at the same time unlike eating at the buffet where some or all of your food is cold by the time you sit down. You don't have to keep jumping up and down refilling your coffee or tea, it's quiet and relaxing, a good way to start your day. If you don't want to sit with a group of strangers, ask for a table size for your group or if there are only two of you, request a table for two, they will happily accommodate you.
The dining room also offers items on the menu that you will not see at the buffet, i.e., baked apples (yum), smoked salmon, eggs Benedict, poached eggs, turkey bacon and corned beef hash made from the corned beef offered in the deli restaurant (order at least two of these, portions are small and it's so good). As with any other food items offered in the formal dining rooms, you can order as much as you want of any items offered.
There are days where you are in a rush to get off the ship but save at least one morning to enjoy a relaxing breakfast in the formal dining room, I don't think you will be disappointed.