Invaluable Add-on! Rated 5 out of 5 stars
In one word: invaluable! It makes searching the web easy and efficient, and doesn't intrude on other aspects of browsing. You won't feel its existence when you don't need it, but once you start typing your search in the Awesomebar, the magic begins!
Try it, really, and you will forget that Firefox existed without it one day.