Rated 4 out of 5 stars
I use this addon regularly in Windows with Firefox 4.0 and have recently added it to my Linux/Firefox 4.0 installation. It works well with only one problem in that the options do not show up in the right click menu when selecting an image to search for.This review is for a previous version of the add-on (126.96.36.199.1-signed).
Haven't seen that before, very unusual... I'll have to take a look, but probably not too hard to fix. Thanks for bringing it to my attention!
Edit: This has been fixed in version 188.8.131.52, which is available from the 'all versions' page. Once it's fully reviewed by mozilla it'll show up here.