I think Mozilla have got it wrong. All these new versions of Firefox leave me cold. I'm still using version 3 which is still supported by Mozilla - I had an update to 3.6.25 in the last day or two. What is the objective and benefits of all the latest versions? The advantages of sticking with an old version are 1. you know how it works without having to refamiliarise yourself and 2. all your addons work without any hassle. If I'm going to try an improved browser I would jump ship entirely to say Opera, which I have tried and been quite impressed, particularly by the speed.
Tony