Ashlee's on formula, and when we had our 15mth Plunket visit, I sheepishly told the nurse that she was still on formula, not cow's milk (just habit for us, and laziness on not switching Ashlee over fully to cow's milk). She said it doesn't matter. As long as they're getting some sort of milk. With the price of cow's milk these days, it's probably just as expensive as formula