Yeah, I don't know that I'd wanna leave one of those running unattended, but they're great for spot heating when you're working though. Seems like a friend of mine hung some of those tubular shaped quartz heaters overhead, parallel to the ground, in her wash room in the barn and said that they did real well.
Tiff leaves heat lamps on in her lean-to for the horses... I've always been a little leary of that, but I suppose it's safe enough in her circumstance, it is an outdoor metal building without a lot of flammables around.