I got one as part of the M deal from B&H a while ago. I recently used it as fill flash on my 6D shooting inside a caboose and a steam locomotive cab (both firmly parked in a museum), firing it over a 24-105 and 17-40. It doesn't provide a lot of light, but is so easy to carry that the occasional benefits may well outweigh the costs (financial and space considerations) if you can get one cheap enough. I haven't yet tried it as a controller for bigger off camera flashes, but understand it has that capability? and will try it out over the next month or so. Having said all that, I don't know that I would have bought it unless it came "free."