After trying Dr browns (which worked fine for our other child), tommy tippee, and nuk bottles for our baby that had reflux and a lot of gas, we gave these bottles a try. She absolutely loves them and we were able to switch between bottle and breast with no issues. They have a lot of different shaped nipples for babies and you can push the air out so they don't swallow air. We also warmed the formula which was different but took no more time than a bottle warmer. We would put warm tap water into a coffee mug and place just the liner with formula into the mug for about 1-2 minutes, then drop back into the playtex bottle. I have had zero problems with leaking, and I do not miss washing bottles at all !! Drop in bottles have been used for a long time for a reason, they work well.