I am using Dr. Brown for my sixteenth month son and will use the same brand for my 2nd baby due in 4 weeks. The ventillation design works fine and I never need to burp my son!
We used Dr Brown for our little one as a baby as well - and if there s a need to use bottles again this time round i will most definitely use the same brand. The ventilation system to prevent wind is second to none, and stopped her crying hysterically after every feed because of wind.