Long time Firefox user. Installed Librewolf today and so far so good. I used Firefox sync to get all my settings, bookmarks, open tabs, etc. back.
At some point I will probably find an alternative yo Firefox sync but it'll do for the time being.
The only thing that sucks about it is some sites just flat out don't work well. For example, in Librewolf I cannot login to my banks website. The site loads, but the login just hangs. Firefox it works immediately.