I just upgraded. It completely changes the chrome of the browser on OSX and it is _absolutely hideous_. There are a lots of unnecessary animations that I find very jarring. I don't know if there's a way to change it back yet.
UPDATE: There is a "Customize Firefox" button which allows modifying the theme, which fixes the colors, but not the shape of the tabs or the animations.
UPDATE: In about:config, you can disable some of the animations with `toolkit.cosmeticAnimations.enabled: false`
UPDATE: There is a "Customize Firefox" button which allows modifying the theme, which fixes the colors, but not the shape of the tabs or the animations.
UPDATE: In about:config, you can disable some of the animations with `toolkit.cosmeticAnimations.enabled: false`
UPDATE: You can bring back curved tabs with this: https://github.com/wilfredwee/photon-australis