Rated 4 out of 5 stars
I found this add-on quiet useful in combination with SearchWP.
I'm not longer forced to use FF search toolbar in order to use quick "find on page" buttons added by SearchWP, Search Synchronizer automatically updates these buttons for me.
I'd give it 5 stars if this addon wasn't pretty much dead.
P.S. I'm using it with FF3, have no issues.