I have been a Firefox user since it was called Phoenix.
This is the best Firefox , but I have lost a ton of extensions including my Vim extensions. So right now I use Qutebrowser and know that the new plugins will get added.
Vimium is _good_ but I really wish it would use the browser's native search widget when searching via `/`. I've been meaning to look into the documentation, but my assumption is that this is a limitation of the WebExtensions API.
The problem with all vim-style extensions is that they have been limited in potential functionality. For instance they won't work in any builtin pages such as about: pages or the new tab page or https://add-ons.mozilla.com. This forces the user to think about whether their command will work or not and induces an uncertainty in their flow.
The other issues regarding limited control over the browsing experience may be resolved with future API expansion, but the previously mentioned hobbling is something with which we are most likely permanently stuck.
[0]: https://addons.mozilla.org/en-US/firefox/addon/vimium-ff/