I don't think batters get comfortable when a pitcher works fast. He doesn't really give them time to get set and relax. But yeah, Sheets has had a tendency to give up homers in his career. By comfortable, I meant they pretty much don't fear Ben missing up and in, or getting wild. They have a good idea where to look for pitches and know he's going to throw them something in the zone. His working fast might upset their rythm early, but by the 3rd time through, most hitters adjust.