imo, breastfeeding is more for the bond between mother and baby bah. If you ask those breastfeeding mothers whose kids enter infant care and/or childcare, most will tell you that their children fall ill too. At least, that's the experience of my friends whose babies attend infant care and are breastfed till 1yr plus.
On the other hand, ppl say that formula makes babies sleep longer cos it takes longer to digest, also not true for my girl. Whether she drinks breastmilk or formula she still demand the next feed at the exact same timing... food for thought. =)