Too bad that Vimperator will most likely stop working once Mozilla deprecate XUL addons in Firefox 57[2].
[1]: https://files.grid.in.th/0EEhIG.png
[2]: https://blog.mozilla.org/addons/2016/11/23/add-ons-in-2017/
I still wish I could have the command line back though. Annoyingly Firefox actually includes some sort of command line thing when I press :, but it seems to be only for web developers. I'd be happy if Mozilla provided a way to extend that so that it could be used for actual browsing...
https://developer.mozilla.org/en-US/docs/Tools/GCLI/Writing_...
I added a command to toggle a preference in about:config that I switch often. It is kind of a pain to write and debug commands for the GCLI though (compared to writing javascript mapping in Pentadactyl).
One of the coolest things about pentadactyl is that I can make any combination of the UI into keyboard shortcuts (or a modular key chord) to toggle visibility when needed.
I used to be a Vimperator user, but lately I've found it too buggy to use. Even the help pages do not function properly.