Oh Dr. Brown, we always come back to these bottles!  Our 4 month old has been using these bottles since birth.  They came highly recommended by my sister who used them for my niece the year before.  The travel caps are great and the little disks to avoid leaks when traveling or storing work awesome as well.  Nipples are flexible yet strong. At first I really didn't think they did much for gassiness.  We had to give her mylicon once in a while.  Then we switched to Ventaire, which was nice due to simpler cleaning but the baby got way more gassy and we had to use mylicon every single day! ...