[autocorr]

That's something I ran into as well, but actually has had a solution in vanilla Firefox for a while. You can create keywords for searches by right clicking a search box and selecting "add keyword for this search", and can then be used in just the same as vimperator by typing that keyword into the navigation/awesome bar (such as with VimFX). One advantage to this is that you can create a bookmark folder of search keywords, and they'll sync across all your devices thru Firefox sync. I find this especially handy on Firefox mobile.

[wsha]

This is a nice feature. The downsides compared to Vimperator/Pentadactyl is that you can tab-complete the search term and you can't get search suggestions as you type (or at least I haven't gotten either of these things to work).