Rated 4 out of 5 stars

Useful add-on. If you ever check Live Http Headers to see what cookies have been set or if you browse the source code of a site looking for all the javascript files then this extension will save you a lot of time.
It still has some bugs as noted on the download page but the developer responded promptly to my feedback so I'm sure they will be fixed soon.

This review is for a previous version of the add-on (0.3).