The plugin breakage is the only downside of the new Firefox, the rest is just awesome.
I'm still looking for a new auto form filler that can have multiple profiles and fills in all fields at once with a hotkey. This is useful for filling in bugzilla bug reports where some fields always get the same data.
"The only downside" Sure. Aside from the number of other extensions that simply won't work in new Firefox. And the lack of any user control to make the browser not work like or look like Chrome.
For Classic Theme Restorer withdrawal, try custom userChrome.css code.