The add-ons should catch up to be compatible with the latest FireFox.
One of the great ones is the spell check that works in the browser, helping you with spelling whether you're writing a forum post as I am now, or writing a blog post.
I also like some of the 'traffic measurement' add-ons, like Alexa and Compete. It is great to see the relative traffic of a site in the bottom of the browser window frame for every site you review - without ever having to look them up.
Those are at
Alexa the Web Information Company and
www.Compete.com, respectively.
I like the feeds, to keep up with what's happening in your online world so you can blog about it.
Regards,
Keith
p.s.: Still have to try ScribeFire