I am a developer on a team of developers for a large data and interaction-rich website and we've watched the stats morph over the past 8 years from 23% mobile to 23% desktop. It's been a very swift revolution. I do a lot of QA on my phone now. I have been a Firefox proponent for at least ten years and resolved to do most of my QA on FF since I was most familiar with its features. Something that is very irksome about iOS is I can't suppress ads on Firefox on ios but I can on Safari. So Safari has become my main mobile browser. I'd love to keep pushing FF into the future- and still use it as my main desktop browser- but I can't advocate its use at least on iOS because of the ads issue.