Hiya!
We started cow's milk (organic whole milk) at around 10.5 months. Here in Canada we are told we can go ahead and introduce milk just a tad before the 12 month mark. Anyway, we introduced it in a sippy during meals at first, then we moved it to the bottle. Now he gets 2 full milk bottles during the day and still gets a full 8oz bottle of formula before bed. Although he's not a picky eater, I like the idea of topping him up on all "nutrients, vitamins and minerals" at the end of the day.
I'm going to continue to do formula at night until he refuses it.
HTH
Nay