For the last 6 months I have only used Firefox for 2 reasons: 1, to get stored logins from Autofill Forms when I find I need them in other browsers, 2, to use the Web Inspector tools. All other times I use Opera as my main browser then Chrome for entertainment. This is because I know my favourite password manager extension is likely to die when 57 is released.
Firefox is next to useless to me without a decent system to manage passwords. Opera at least provides a VPN and browsing is smooth.
Unless FF 57+ offers Opera like features I will continue to use FF 56- for legacy services. If Opera gets FF quality website inspector tools and a good password manager then I'll likely not need to revert to FF in the near future.
Looks like FF has killed itself.