Rated 4 out of 5 stars

Although the default Firefox developer tools have really improved in the last few years, I still treasure Firebug for its numerous integrations of add-ons and unmatched structured DOM view. It might take a second or two to open if it's not running, though, which is a consistent nuisance. Still, a very good add-on for client-side development.

This review is for a previous version of the add-on (2.0.2.1-signed).