Since Snowden (and even before that) I use Tor for my browsing that isn’t video or fancy Javascript commenting or whatever bullshit. And since the update function doesn’t work with Tor (you have to redownload the bundle everytime they update something) it’s nice to have a way to get your stuff from the old Firefox to the new one. And while there is FEBE to backup addons and I think there’s also a way to save all open tabs to bookmarks and then just reopening them there’s an much, much easier way to do this:
Copy the user-profile!
This is dead-simple. On the old version go to Help > Troubleshooting Information and click on Profile Folder | Show in Finder. Close the browser and open the new one. Do the same thing again and copy the old profile (if you haven’t messed with it it should be profile.default) to the new one (DON’T FUCK THIS UP).