Was pretty dang easy! (And thank God for that - we could use a little more easy peasy in this house!)
Lu had her first taste of cow's milk five days before her first birthday, and was transitioned after just two days. No special timing was used; we happened to be approaching the end of our present can of formula, and I didn't want to buy another. The first swig resulted in her classic EWWW, what the eff?! face - probably due to the drastic change in temperature. (I had started giving her room temperature formula months prior, but refrigerated milk is downright cold.) So I played around with different formula-milk ratios over the next two days, until all the bottles were eventually just milk.
We were verrry fortunate, as Lucy has shown no sensitivity to dairy, no fussiness or tummy troubles! Our pediatrician said to keep the milk intake between 24-32 ounces each day, which hasn't been a problem. She seems to really like milk much more than formula. Now if only we get over her aversion to sippy cups.........