As someone who uses Firefox for work everyday because its needed for my job, I'm just here to say its trash. It has been going downhill since version 28. Literally been using it since version 2 and what people used to love was the complete customisation of everything and powerful extensions. All was lost when they killed legacy xul based extensions and started locking down elements of the interface you can customise. It also seems slow in comparison to chrome and cant handle as many tabs, mobile versions of the browser suck too.