I love being able to easily navigate between tabs (a/J and s/K for me), go back/forward (h and l), open the current tab in a new window, close the current tab, etc. though (of course) the killer feature is "link highlighting" or whatever it's called. You can also enable "link highlighting" where selecting a link copies the URL. I also find that occasionally useful!
I also found it useful to have a link bind that just focuses the link element, often that can open up hover menus or trigger other focus/hover CSS changes.
I can't use the web without vimium.