Instruct: Classify Amazon reviews into positive or negative sentiment
Query: Not too keen about Avent bottles

I tried the Avent bottles and they were really awful. First thing is that they create a terrible negative suction pulling-pressure while the baby is drinking, which is frustrating for the baby as it does not allow the food to flow freely through the nipple. It also causes the baby to suck air, causing severe gas! The negative suction pressure also creates a terrible noise, which is oh-so-annoying to listen to!!!!! Also, the nipples are made of a hard plastic and it started to create blisters on my son's lips from all of the hard sucking!!!! I switched to the Dr. Brown's bottles and they are much, much better, eliminating all of these problems! I tossed these bottles straight into the garbage! Don't waste your money!