When he was younger, LO liked the Breastflow bottles. Around 12 weeks, not so much. We're using the Playtex drop ins right now, but hope to transition back to Breastflow. The Playtex system is extremely cheap, but a lot of waste with throwing away those liners all the time. LO went easily between Breastflow and breast, but these days is fussing at the breast until the letdown, so I think it may be time to get him off the Playtex bottles, even with slow flow the milk is immediately there, and he may be developing a preference.