YES! they really do work!
I didn't want to change bottles as I had just gone out and bought all brand new Avent bigger size ones, but bought 2 Dr Browns to give them a go and they are fab! So went out and bought another 4!
The cleaning is easy too, but I would recommend buying a proper Dr browns bottle brush, I used my Avent brush for ages and only recently got a Dr Browns one and they are soooooo much better!