Everyone has a list and a love of AddOns and Extensions for Firefox and Google. I am no different. And I have gone through the period of time when I have a lot of them, and when I have less of them. What made the largest difference in my use was when Google made it so Chrome syncs, which ends up auto-installing in new Chrome installations easily, although not the settings inside each extension. And with Firefox I mastered FEBE with Box.Net to install profiles on new installations of Firefox.
Some extensions/addons are complete tools in themselves and some simply provide something that was missing and augments the actual browsing experience. Highlight to Search which allows you to search keywords by highlighting instead of typing them into a search box is one of the latter.
I am enjoying this extension and it is setup in all my browers as they sync. I am having minor issues getting i to work for https pages, despite setting the options for this function. But it is so nice, try it out.