The reason why I use Firefox - Instructions for all Firefox versions read this! Rated 5 out of 5 stars
I have been using this add-on for years now and it is the main reason why I pick Firefox over other browsers out there. I cannot browse without this add-on. It makes browsing more accessible and easier. I recommend it to everyone.
This may have been mentioned earlier, but to those that wish to have it to work with any FireFox version download the tip.xpi file from here: https://bitbucket.org/satyr/ubiquity/downloads and open it with Firefox. It will install it and it will work even if you update Firefox to newer versions.
I hate to see that people rate this add-on to oblivion just because they can't find a way on their own to make it work with newer versions of Firefox. Support from developers is important but this particular problem is no reason to rate this add-on in such manner.