I'm planning on splitting my browsing once I upgrade to FF 57; it's pretty pathetic since I'm already having to do so much browsing on Opera & Chromium now because so many websites are broken on FF, and I don't expect them fixed, even with the Quantum wheel-spinning.
My side add-ons like Scrapbook & Firebug are still working over on Waterfox (although not PaleMoon, which has collapsed in terms of add-on support), a fork which will hopefully support add-ons well into the future.
https://www.waterfoxproject.org/downloads
Also, the Extended Support Release of Firefox will support add-ons for several more months (though looking into the development version isn't a bad idea, depending on the add-ons in use).
https://www.mozilla.org/en-US/firefo...nizations/all/
I don't know what the status of really good add-ons like GreaseMonkey will be, long-term, however.