Mozilla Firefox 78.0.2 Fix is now available, and subsequent 0.x releases after the official release will primarily lead to some bug fixes. Firefox 78, while not a big improvement, has improved the user experience, for example by adding a refresh button to the uninstaller that allows Firefox to revert to its original configuration, while also having a PDF reader built in and giving up support for some older operating systems.
The list of specific updates is as follows:
Fixed accessibility regression in reader mode (error 1650922)
Make the address bar more elastic to corrupt the data in the user profile (error 1649981)
Fixes regressions that open some external applications (error 1650162)