Works Rated 5 out of 5 stars

Works. Much better than Chrome's Instant mode.
Tested on Aurora 13a2 (Fedora/Win7 (both x64))

Still no HTTPS Everywhere compatibility. Hence -1 star.
Also, can't synchronise custom engines and parameters between computers using Firefox Sync/Weave

UPDATE:
The developer replied!
I tested out the new version and it works splendidly! (I faced the missing googlebar bug too, but thought that it was due to the plethora of addons installed on my fox)
HTTPS everywhere works well too!

Now onwards to Sync, please!
Also, how about Mycroft integration?

This review is for a previous version of the add-on (2.7.0).  This user has other reviews of this add-on.

Hey Sagar,
<br>did you check 2.7.1. (currently in review process)<br>HTTPS Everywhere compatibility should be fixed! :)<br>https://addons.mozilla.org/en-US/firefox/addon/instantfox/versions/?page=1#version-2.7.1<br><br>

Concerning Sync, it's on our ToDo, but currently not priorized, because we need to tune some other features, first!