It took a slow transition of one sippy feeding a day. Followed by a lot of milk on the floors, hair and walls! He would not accept the sippy with the "stopper" in it. He still throws it on the floor from time to time but he is drinking it almost every feed now. Too bad our Air Shipment STILL has not arrived yet...because I only brought 1 YES 1 sippy cup. I really thought Air Shipment would only be 2 weeks (not 3+!!!) and I didn't think he was quite ready to give up the bottle.
I refuse to buy any more since we already have 4 or 5 different kinds ;-)
Here is a pic of M with his sippy