I've got one of those, but it's not brighter than several of my other lights. I didn't use it for very long because it's a pain in the rear. The MagicShine, which just runs off the same battery as my headlight, is actually brighter and cost $30. The Knog Blinder 4V is about as bright, though it has the problem of a weird mounting system and the battery only lasts 2 or 3 days.

At night I run the MagicShine on the rack on constant, and a Knog Blinder 4v on the seat post flashing and a Cygolite Hotshot on the helmet in flash mode. In the daylight all of them are flashing.