From what my doctor told me, the fat in milk is a very important brain developer in children, in addition to the well known need for calcium. That's why they tell you to use whole milk, not 2% or skim. You don't want you little guy getting bigger and prefer formula. It's too expensive, he gets what he needs from food now, and his body needs what milk can give him.
My 3 year old had some trouble switching to milk. We breastfed for a 11 mo., I thought I'd try giving her a little milk from my glass one day, (I remember thinking, what's a couple more weeks), and within 1 minute she vomited a LOT !! and she broke out within 30 seconds with red blotches around her mouth with most dairy. She could tolerate swiss cheese melted on toast, and yogurt, I believe. My doctor told me to keep nursing, and giving her things she could tolerate. I had to try milk again every couple of months. I think it was 15 or 18 months that she was able to tolerate more dairy, and then she just didn't like milk. I think around two she drank mildly flavored chocolate milk, which she continues to do today. I buy the syrup and mix my own. The pre-made choc milk has way too much sugar per serving for me. I don't know if the sips of milk that I gave her a couple of weeks before she was one, created an allergy or not. Their tummy's just aren't ready to digest it yet I guess.
Here's a link for a Freihoffer's outlet near you.
http://freihofers.gwbakeries.com/outletResults.cfm
I've found they carry hormone free milk, cheaper than my local grocery stores, and/or economy grocery stores in my area. Also everything they carry is approximately 1/2 the cost of grocery store prices.