Bottles I have used/tried: Avent, Nuk, Playtex Ventaire Advanced (wide & standard nipples), Dr.Browns.
Avent: This was the first bottle we used. A girlfriend of mine had given them to me and highly recommended them. When we had a latching issue, this was the bottle I had given my DD to supplement formula on and since giving DD the bottle she has refused my breast. I found the nipple (size 1, the slowest flow they have) to drip a lot of milk when turned upside down. DD didn't have a problem with these bottles in the beginning, and was downing 3oz in under 10mins. Eventually they became a problem, and DD started to get gas pains. That's when I decided to play with bottles to see if it'd help.
Pros: I love how these bottles look. I never had an issue with them leaking.
Cons: The nipple was too fast for DD. The bottle(with the wide nipples, too) had given Lara preference to bottle over breast.
Nuk: The next bottle I tried was Nuk. We did not get very far with this one as the orthodontic nipple did NOT go over very well with DD. I made sure to have the nipple placed correctly in her mouth, and it took her forever (I think 20mins was how long I tried) to even get 1/2oz into her and she became a cranky girl. Not sure if it was she didn't like the shape of the nipple or if the flow was too slow for her. DD however did not have her "episode" after the bottle
Pros: Not really sure on this one as I didn't give the bottle much chance. I guess the orthodontic nipple would be a pro.
Cons: Too slow of flow.
Playtex Ventaire Advanced: We tried this bottle next, and tried both standard and wide nipples to see if there was much difference. The first bottle I used was the standard nipple and I noticed a great improvement in DD's comfort level, although she still had gas pains, and was still eating way too quickly (2 1/2oz in under 10mins--no lie). I had gotten a wide nipple to see if there would be a difference in how slow it'd get her to eat, and I found that immediately she was much more uncomfortable and cranky after eating. I'm not all too sure if the standard nipple I used first had caused further laziness on DD's part or not.
Pros: There was a marginal improvement in DDs discomfort with the bottle, and even still a marginal improvement from nipple to nipple.
Cons: Still caused DD to be uncomfortable enough to make me want to try one more bottle.
Dr.Browns: The last and final bottle I will ever be using. In a desperate attempt to relieve my little girl's discomfort, we made a trip out today to get this bottle. And I have to say, wow! I'm impressed. I've given her 4 feedings from this bottle, and it's a complete 180! Yes, DD still is a little bit gassy, but I'd have to say she's honestly 95% better. There's no more scrunching of her features when presented with the bottle, and no more "mommy your poisioning me" faces as she's eating. There is no going beet-red in the face, clenching her fists, kicking her legs, drawing them up to her tummy, grunting or groaning anymore. I noticed she is not nearly half as hard to get to burp, although she is still a difficult burper. I also noticed she's passing wind easier as well, but this could be she may have finally figured it out as well.
Pros: With my DD, this bottle actually works. The bottles I picked up (the glass ones, not sure if any of the plastic ones were as well) were made in USA which is a big deal in my household as we are trying to support our own economy as best as possible. Our rule is North American made (Mexico included, Canada preferred over all else) unless we absolutely cannot find it. The glass is also a plus for me as I know for sure there is no BPA in that.
Cons: I personally do not find the extra pieces a bother but I suppose I could see how they would be. The glass bottles are bit bulky. Pricey, but still worth the extra money in our case. There is not enough variety in multi-packs (i.e no starter kit like the Playtex Ventiare Advanced).
I would highly recommend the Dr.Browns to a friend, and plan to do so as two of my friends are expecting.