Infrared quartz heaters--do they really work well?

I have been deluged by Eden Pure and several other companies, plus I see in Parade and US Weekly Sunday inserts the ads for the quartz infrared heating units. They are portable, "run on less than a Mr. Coffee" a day, etc. Right now the adds seem to be for the same product, just packaged differently. They all rely on convection, infrared bulbs, and some copper concoction that retains heat. They seem to come in two sizes, one will heat 300 sq' and the other 1000 sq'.

Anybody out there using one and if so, are they worth the cost, which is 300-400 dollars? Are they efficient and work as well as the maker claims? Opinions would be appreciated.