Rated 2 out of 5 stars

Excellent BUT not for laptops yet unless you plug in a real mouse instead of using the touchpad.
On a laptop with touchpad, use instead the extension "Mouse Gestures" which is perfect for instant zooming and dezooming with the touchpad (just edit rules and make sure you set a very simple rule for it... like for instance 3 for "zooming image size" and 1 for "cancel zoom") then apply your rule directly upon the image... fast and no brainer (make sure your apply the rule "on" the image... don't start your line from outside the image otherwise you'll might be disappointed!).

This review is for a previous version of the add-on (0.3.1).