After I discovered extensions/addons for vim-like control of browsers few years ago, I've completely changed how I browse the web. I rarely even use the mouse anymore. Only when I want to save an image or save a file (from a misconfigured server that doesn't auto-download) do I still use a mouse. For everything else, you simply don't need a mouse at all.
Vimperator is the king among Vim-like keyboard shortcut enabler extensions in browsers, sadly it may not work in the future versions of Firefox because Firefox is transitioning from highly free but less safe/performing XUL based extensions to a safer but limited WebExtension model. It is very fast and smooth with lots of features.
I used vimperator and experienced crazy slowdown on Firefox in both OSX and Ubuntu. This happens after you browse for a while. Wasn't sure why initially. Things improved dramatically after reinstalling the addon. But I had to do it frequently so it wasn't worth it.
I think it's because things are saved in history for a long time or history chain of sites in a tab is very long.
Edit:
Only extension that is vim-like that hasn't let me down is cvim for chromium/chrome.
I'd heard about these before, but never tried them since I assumed there would be some case in which they didn't work, and it would be enough to be a deal-breaker.
But after reading this sub-thread, I decided to give it ago, and I've been absolutely blown away, such a pleasurable experience!
I've started using Feedbin for my RSS feeds lately, which makes great use of vim-bindings, and I've enjoyed using that site more than any other partly for that reason. Now I get that on every site - and as a bonus, adding an exception (so that I could continue using Feedbin's bindings) was easy.
The only thing that seems to be missing is a way to edit large text fields (like this one) in vim-mode. Though I understand there are separate plugins people swear by for that, so perhaps they work in conjunction, I'll have to explore that next.
I wish there was something like Vimium for Windows 10. I am trying to use hotkeys whenever I can, but some applications are expecting you to use mouse. In such situations I would give gold to be able to quickly select and click elements on screen by keyboard.
Do they help navigate the dev tools? The web pages I'm developing are all UU- and keyboard-friendly, which is great when I test them. But I'm having a hard time not reaching for the mouse because I need to use the devtools.
1) Impossible to navigate some sites 2) Slows down the browser to a crawl over time
Generally, not a usable long-term solution