This is an amazing extension, even if you don't use vim for everything:
If you're at least somehow familiar with vim keybindings you'll quickly adapt to vimium, which main point for me is using less mouse and more hotkeys.

It has two main issues for me:
It doesn't work everywhere (for example in Jira i can't navigate the board with vim keybinds)
It doesn't support editing with vim keybinds which is understandable and idk which behavior would be more usable, but still can't help but insert some j's and k's into posts

I simply LOVE this add-on. On which buttons it works depends on the website, but it works for 95%. It doesn't work on 'special' websites like this one (firefox add-on site).

I've been using it for several years now. It's great. Totally 2nd nature. Highly recommended for keyboard jockeys.