On my end, I never actually stopped using Firefox after Chrome came out. I had Chrome installed and used it mostly for testing and validation of web code, but my day-to-day was Firefox. I had my extensions configured and setup in it and my large collection of bookmarks was there (I guess I was just too lazy to import them into Chrome). I think the main reason I stuck with Firefox was because I used Android and the Firefox browser on Android supported my extensions -- the most important being uBlock Origin, so the browsing experience was better even though the overall performance wasn't great -- and since my bookmarks were synced, it just worked out better for me that way.

I ran Developer edition, so I received the updated that killed most of my extensions earlier than most and I realized that the main reason I used Firefox was because of my collection of extensions -- many of which now didn't work. So I abandoned Firefox on all but mobile earlier this year and switched to Vivaldi (chromium based)[0].

Now that my most important extensions are available (though still haven't found uBlock Protector), I've started using Quantum again. I'm really enjoying the fact that HTML5/Flask autoplay can be disabled in "about:config" (and that it works, unlike the myriad of extensions I installed for Vivaldi claiming to do the same but which mostly broke things like gifv playback and random non-YouTube video sites that would still autoplay or would simply refuse to play). Firefox Quantum is faster and I'm back to being a (mostly) happy Firefox user, again. Last night I removed the icons for Opera and Vivaldi from my task bar to keep me from accidentally starting them due to muscle memory (and therefore adding bookmarks in a place where I will lose them).

[0] No, I don't have a thing against Google, I just preferred the high-degree of customization that Firefox/Vivaldi gave me over Chrome. I don't like Chrome's opinionated configuration panel -- I'm a developer and I like knobs to turn. Though Vivaldi lacked the conveniences of syncing things between my various machine so I ended up on Opera rather regularly.