I also feed a grain-free food, Taste of the Wild, Pacific Stream. I'm thinking about switching to Natural Balance though, b/c the TOTW makes the dogs smell REALLY fishy! Otherwise, it's a great food.
Dogs don't need grains. More grain = more poo b/c it goes undigested. Corn is especially bad for dogs and is in most of the cheaper foods (sometimes the number 1 ingredient! :mffad