I stopped using Firefox after the 3.x period. I personally believe 3.x series was the best Firefox, and that going forward it has only been downhill. On the consumer level, I think their biggest mistake was giving each release a new major number (4,5,6,7,8,9) when only minor things were changing. We went from Firefox 4 to Firefox 10 in less than a year. Why would a consumer like so much implied change so fast?