I love the vi approach to text editing and have been using it in my daily work for 20 years now -- 10 years in Vim, 10 in Emacs, thanks to evil-mode -- and I have no intention to switch to anything else. However, I tried Vimium and other vi-like UIs for web browsers on multiple occasions but surprisingly it never stuck even though it seems so logical to use it for that as well. Eventually I realized that I actually enjoy taking an occasional break from the vi system and using the mouse for a bit. It's relaxing. The other thing is that web browsing as a task is so different from text editing than many vi concepts do not translate 1-to-1 and there's just too much new stuff that one needs to learn to make it work for web browsing. As a result the cognitive and muscle memory savings are really not that big.