Rated 4 out of 5 stars
Great extension. The only reason I gave it 4 starts instead of 5 is because there are some minor bugs. Things like selecting some text and pressing Ctrl+F will put it in the Find window, but when you hit Next (or F3) it reverts to searching for the previous text.
One feature request I would make would be for pressing Ctrl+F3 to start searching for the currently selected text, without bringing up the Find bar. Ctrl+F3 is a standard in most apps to search for the selected text. So same as Ctrl+F, but without bringing up the Find bar.
There are a few bugs in the latest versions of firefox that I'm planning to fix of course, but haven't had enough time to work on the add-on lately, so they might still take a while as there's a lot to do in the add-on.
Hitting F3 (no Ctrl) should already find the previous text without bringing up the find bar. If it doesn't, that's another bug that I need to look into (it works for me right now though).