We use rice milk for my son.
Our pediatrician did not recommend it. I have lactose-intolerence issues, and so we started him on this. He does eat cheese.
I also think rice milk is great because cow's milk often aggravates cold symptoms. When my son gets a cold (quite often this winter, as he's now in preschool), I don't have to switch milks. We can quit dairy for a while without it being a 'big deal' for him to go from cow's milk to rice milk. And we do supplement with a multivitamin so he gets calcium.
I'm also not a fan of factory farming or factory dairies. Cows are often given hormones to produce more milk. These hormones, in my opinion, are not good for developing boys. Even if we buy hormone-free milk, it's more expensive than the rice milk too.
Organic rice milk is available. We can buy it at nearly any larger grocery store we go to.