I remember using the original keyboard productivity extension for Firefox, "hit-a-hint"[1] back in Firefox 1 & 2. Since discovering vimperator after, it has been an essential extension on par with an ad blocker. However, I found it consistently broke on new releases of Firefox and could take months to fix. Pentadactyl wasn't any better in this regard. For example, the current extension page says it only works up to Firefox 38! I eventually switched to the less powerful extension VimFX[2] that can run on newer versions of Firefox. It has more than 90% of what you use in vimperator: movement, hints, and tab management. And really, things like the vimperator extension bar were made for a time before the awesome bar, which can now do things like completions, searching with keywords, and switching focus to other bookmarks or tabs. It will be sad to see it go when Firefox finally deprecates XUL based extensions, it's like a piece of history!
[1] https://addons.mozilla.org/en-US/firefox/addon/hit-a-hint/
[2] https://addons.mozilla.org/en-US/firefox/addon/vimfx/?src=se...