The new version (since firefox 57) has lots of problems. Missing features, signs out almost every time I close firefox (despite setting options to NOT sign out), will not autofill many login pages, but maybe the biggest is that it uses TONS of memory, slowing everything else down. I was just testing it with about 15 tabs open and lastpass disabled - when I would enable the lastpass add-on my memory usage would jump by well over a gig!