Rated 4 out of 5 stars
Great add-on. The only problem I see is if you want to add TAB characters in the search text box... would be nice to be able to use SHIFT+TAB or maybe provide a toolbar with these kinds of characters...
There is a helping popup, which is available when you press Ctrl+Space after entering a backslash.
In previous Firefox versions this was even shown automatically, though there's currently a bug avoiding it to do so.