While I'm at it.
I utterly abuse every form of fuzzy-matching autocomplete I encounter, which is why I'm a terminal zsh fan (see what I did there?); one of the coolest UI experience I had in a browser was with the Viperator plugin on Firefox. The few letters controlling the few navigation features I used were juuuuust at the right place, and hitting t or o to autocomplete the url of the page I wanted or to autocomplete the web search syntax shorthand it provided was immediately natural and extremely fast and fun to use. With the caveat that whatever questionable website or search query I typed in tended to stay rather high in the autocomplete matches. With awkward results. But that's my problem.
It has a shorthand that puts a numeric id on every link and allows (what else) fuzzy-matching autocompleting them, as a mean to replace mouse clicks, but I never really got the hang of it. The numeric labels were really invasive, and I almost always had to use the numeric key as I almost never got the matcher to select the link I wanted quickly enough; I just used my nipple mouse instead. Which is sad because I really liked the idea; the implementation was just not quite good enough.
It was missing a few features that I consider pointy enough to have to script myself, for example, I wanted keyboard hooks to save images, text copy-pastes and stuff, in a directory set in advance or specified on the spot or whatever, but since Vimperator uses vimscrip (or a subset thereof, I don't recall), I never made it. Actually I can barely script my actual vim, but that's besides the point.
It was supposed to open my editor of choice on a certain keyboard hook in text fields, but I never got it to work, which is a shame; I really wanted that feature. There's a built-in vim-style editor, but I never got the hang of the modal transition in and out of it, so I never used it.
In the end I stopped using it because it was f%$king slow; having the browser freeze for several seconds after a keyboard shortcut makes the shortcut moot, you see? The keyboard focus also tended to be hard to follow; the worse being (I know it's now Vimperator's fault) flash, which captured the focus so hard I had to click on the page to get my freaking focus back. Sometimes to get it back in some random mode I don't care about, which made me develop the habit of smashing escape all the time not only once, as I already do in Vim, but several times. Just to make sure. Whenever I wasn't trapped into the raw input mode.
(Edit: it got gradually slower and slower, but out of the box, FF + Vimperator on my p.o.s mid '00 laptops was already, uh, not this fast.)
So I'd say that my perfect eternal browser would be a cleaner subset of Vimperator, lightning fast, with a functional and efficient set of navigation/link-clicker bindings, without Firefox's huge baggage of UI bloat, and with a healthy dose of It Just Works.