We weaned DS from bottles at 11.5 months, since he'd be transitioning to the Toddler room at daycare right at 12 mo. I didn't want him to be going through too many changes all at one time.
The worst part of the weaning process was the first time I gave him a sippy instead of his morning bottle. He FLIPPED! I was surprised actually, since he had been using sippies regularly. Apparently he was really attached to that morning bottle. I just stood firm and gave him a sippy again the next morning. He squawked a little, but that was the end of it.
It was also hard on him when he saw other babies in his room at daycare still getting bottles. He was out "out of sight, out of mind" kid, and he'd only get upset when a little girl had the same type of bottle he used to have.
All in all, it wasn't difficult for us. GL!