Quote:

If you want fast, try the new Firefox (57.0). It's a complete rewrite - virtually a new browser, and it's VERY fast. But it does mean most old extensions no longer work.

I've been using Firefox 57 for over a week now and unfortunately I haven't seen any increase in speed over Firefox 56! :-(
BTW I've managed to replace incompatible extensions by new or updated ones. :--)