J.Z.
I say don't stress over it. When we tried to transition my daughter to a sippy cup, she really fought it. Once we made it not a big deal, it seemed to go easier. We just offered a sippy cup, and if she got upset we gave her the bottle. By 14 months she just had milk in a bottle, and water or juice in her sippy cups. By about 18 months she was done with the bottle.