I am finally switching from Firefox < 57 and Vimperator/Pentadactyl, almost two years after the Quantum apocalypse. So I’m in search for a good replacement. I am giving a try to Firefox 68.0.1 with Tridactyl 1.16.2pre3053 (and Tree Tabs, for that matters).

The conclusion is that you’re fighting against Firefox sandboxing on nearly any point, and no matter what you do, that’s a lost fight. First, of course, you must install the Native Messenger to do anything useful, but that won’t be enough.

Some of the major issues due to limitations of WebExtensions are documented by the extension itself.

— Tridactyl does not work while the current tab is loading, bindings can only be used again when it has fully loaded (even bindings for switching tabs or closing tabs).
— Tridactyl does not work on some pages, including the “about:” pages, the AMO website (a suggested hack does not seem to work anymore), the Reader Mode, source views and image views. This breaks the keyboard navigation workflow, mostly cancelling the benefit of the extension.

But there are many more issues or lacking features, which may or may not be due to WebExtensions. I rank them here from more critical to less critical.

— There are no search suggestions in the command line (yet ?) [S]. To me, that was Vimperator’s killer feature. I simply cannot live anymore without a random access to Wikipedia articles, words definition in my favorite dictionaries or locations in Google Maps.
— I cannot jump to arbitrary tabs with gt (although that should work, according to the doc). Moreover, the option to show numbers on tabs only works on the native tab bar, not on Tree Tabs display. Besides, the g0 and g$ bindings (jump to the first and last tab) ignore Tree Tabs’ groups and jump to the first tab of the first group, or to the last tab of the last group (while gt cycles correctly insides the current group).
— Ctrl-w cannot be rebound [W]; as a consequence, I keep closing tabs accidentally while trying to erase text in the command line.
— Tridactyl regularly loses focus in favor of some GUI elements such as the address bar (this happens when opening tabs with Ctrl+t). You have to click on the display area or press F6 to re-give it focus.
— There is no incremental search (yet?) [I].
− There is no permanent status line [L]. This means you cannot see half-typed bindings, and for seeing the current URL and the target of links you are left with Firefox’ address bar and Firefox’ link-hover display (which routinely shows up above the command line).
— Tridactyl shows messages in a hackish and inconvenient way (no multi-line output).
— Changing almost any setting requires to restart the browser to take effect.
— Documentation is lacking on the effect of available options for “:guiset”.
— Tridactyl needs to hijack the home page to be able to inject its code.

On the plus side, some nice features that I noticed during my short experiment:

— There is a dark theme.
— Alphabetic hints improve comfort of navigation over Vimperator’s numeric hints.
— Tridactyl comes with a large number of search keywords preset (including obscure websites such as the Gentoo wiki).
— The yanking feature looks cool (you can yank the shortened/canonical version of the URL, or the title of the page, possibly as a Markdown snippet).
— Looks like you can do many things with bindings, since you can run Javascript code (but I didn’t try it, neither did I try to do custom bindings when I was using Vimperator).

In short, Tridactyl could be improved with features that are currently lacking, but overall you’re in a state of war against a browser not willing to let you change the UI. They say Tridactyl is the closest replacement for Vimperator. If that’s true, then all those issues are the price to pay for an up-to-date Firefox. See whether that’s worth it for yourself. As for me, I believe I will try out alternative browsers, or stick again to an outdated Firefox.

[S]: https://github.com/tridactyl/tridactyl/issues/140
[W]: https://github.com/tridactyl/tridactyl/issues/1428
[I]: https://github.com/tridactyl/tridactyl/issues/1612
[L]: https://github.com/tridactyl/tridactyl/issues/210