Last week (March 7th) we decided it was time to attempt a sippy cup.
We choose the Advent 4 month Trainer cup, as it has an interchangeable nipple and sippy cup lid.
We started with the nipple and he did pretty well with it. He was able to hold it and put it into his mouth (of course EVERYTHING goes into his mouth, so this wasn't surprising). He wasn't nearly as interested in the sippy cup topper, which I'm guessing is because he had to work a little harder for his milk.