Are these the ones?
We sell them at the store that I work at and I've heard lots of good stuff about them. I didn't know about them when DD was a babe so I have not used them.
We often recommend them if a babe won't take any other bottle. My boss is a lactation consultant as well as a store owner and brought them into the (her) store after a lot of research, so I would expect them to be a quality product. She is quite a "lactivist" so any bottle feeding gear is very carefully researched before being allowed into the store.
We have a hard time keeping them on the shelf as they are very popular.