Product review (4 stars): I've been missing out on this....
Got it today, installed it and tossed a load of wet clothes in the dryer and turned it on with the damper set to blow into the house....Wow!  I never realized how much heat was being wasted just blowing through a hole in the wall!  If you have never seen one of these working it is just like a heating vent from a forced air furnace!  The actual construction of the whole thing is pretty cheap and a couple of ears molded onto it would have been nice for screwing it in place on the wall.  I drilled a hole inside at the back of it and secured it in place with a couple screws. It seems sturdy enough I guess, time will tell. ;-)