For any other Vim addicts out there, Saka keys seems to be the most feature-complete and stable Vim-key interface to Firefox right now (a decent replacement to VimFx, if you ever used that). The feature I use most is link hints, I press the hotkey and every link on the page has a short unique code like "CU" or "FK", and I can press that code to open that link (in a new tab if I used the hotkey that does that). It's also nice to use j and k for scrolling, J and K to move between tabs, d to "delete" (close) the current tab, etc. I rarely have to use my mouse when in Firefox, with this. On the opposite end, there's Gesturefy, to do a ton of browser actions with mouse gestures, clicking and dragging your mouse in different shapes. Tree Style Tab is so basic to my Firefox usage I almost forgot that it's an extension. Vertical, collapsible, tree of your tabs that helps so much with keeping your tabs organized and easy to find, once you have more than 20 of them.