Thank you for your work. I'm currently a tridactyl user. However I'd like to point out that none of these replacements can currently compete with the previous extensions in term of usability.

Simply put, you cannot count on the keyboard shortcuts to work consistently throughout Firefox. They do not work in built-in pages (such as errors). They do not work when inside an input field in GTK. There's no way to consistently override built-in FF shortcuts that simply get in the way.

It's pretty sad for users which expect the keyboard experience to be consistent. I now mostly use FF's own shortcuts for most of the tab-management actions, since those are the only ones that work most of the time when an error page is generated.