Works. Rated 5 out of 5 stars

Works. Much better than Chrome's Instant mode.
Tested on Aurora 10a2 (Fedora/Win7 (both x64))

Still no HTTPS Everywhere compatibility.
The developer still does not ever write the revision history / changelog when updating. hence -1 star.

UPDATE: He did reply! And finally added a changelog too!

This review is for a previous version of the add-on (2.4.2).  This user has other reviews of this add-on.

Sorry about HTTPS Everywhere, there were more urgent bugs for this release! Changelog: https://addons.mozilla.org/en-US/firefox/addon/instantfox/versions/