(not sure where my old review has gone...)
Definitely one of my top extensions. Adds a lot of efficiency to searching. Unfolds it's real potential, if you use a lot of search engines for more specific searches. Very nice and competent developer, he always had an open ear for useful suggestions. Keep in mind: Mozilla is blocking several possibilities for such an extension, so there may be some quirks. Being a developer myself, I can assure you, the developer does his best to circumvent such problems.