Very useful Rated 4 out of 5 stars
Surferby, you can install the official Firefox Addon "Add-on Compatibility Reporter 1.1": http://addons.mozilla.org/firefox/addon/add-on-compatibility-reporter/ With that you won't have to worry about compatibility errors with totally valid addons.
About "Screen Capture Elite", it has been very useful to me in many times. Maybe, as Surferby said, it should have a better version compatibilty control, now that Firefox policy consists on upgrading almost once a month (!).