SmarterFox, one of my favorite Firefox productivity add-ons, recently updated to version 3.0. In the process, it added a new feature, fixed some miscellaneous bugs, and changed its name to FastestFox.
For a major version upgrade, changes are slim. The most notable new feature is the ability for FastestFox to automatically surface related search results from Amazon and OneRiot at the top of a Google results page. The related search results show up in addition to an original SmarterFox bar that lets you repeat a search on OneRiot, Amazon, Yahoo, Twitter, and Delicious. The FastestFox release notes are quick to mention that you can disable related search results.
For as much as FastestFox can do, I'm not particularly thrilled with either the name change--always a pain for users--nor the pushed search results, which outmaneuver Google in grabbing your eyeball at the top of the results page. That said, the extension doesn't crimp any of the app's original usefulness; just its own branding.