I don't believe that breastfeeding is all it's cracked up to be. Even with my limited science knowledge, I know that experiments must have a control. A breastfed baby vs. a formula fed baby is not enough of a control. There are too many other factors there.
DD was mostly formula fed. She was fed 50-50 up until about 8 weeks, then all formula after that.
But she also has good genes (IQ wise-not to toot my own horn). She has a teacher for a mom. She has two paretns who play, talk, and read to her non-stop. She is in a home setting at daycare where she is talked to and read to. She has over 30 words, about 10 "signs", and is very advanced with her motor skills.
She is rarely sick and the one time she had a cold she was actually teething (we now know that her molars coming in cause a runny nose-the top ones are coming in now and her nose is runny again). She's never had an ear infection or pink eye. Never has been on any meds for any sickness.
I've never met one formula fed baby who was behind or overly ill.
I think that people who look down on formula feeders suck. My feelings are-feed your baby. Love your baby. Love yourself.