If anyone wants to help out with any of those issues the respective bugs are:

Rubber band scrolling: https://bugzilla.mozilla.org/show_bug.cgi?id=1124108

Downloads in Finder: https://bugzilla.mozilla.org/show_bug.cgi?id=909760

Toolbar movement in full screen: https://bugzilla.mozilla.org/show_bug.cgi?id=738335

Pinch to zoom: https://bugzilla.mozilla.org/show_bug.cgi?id=688990

Animate back gesture: doesn’t seem to be a bug for this.

Animated checkboxes: can’t find a bug for this either.