Rated 4 out of 5 stars

Nice extension!

It works great except the "Quality" setting which seems to be saved in preferences but not restored.
This behavior happens only in Firefox 3.0.* branch, it works with Firefox 3.5+
To make it work in Firefox 3.0.14, I have simply added preference-editable="true" attribute on element in your config.xul
That does the trick.
It seems there is a bug with the element, have a look at:
https://bugzilla.mozilla.org/show_bug.cgi?id=499105

This review is for a previous version of the add-on (1.5).