Anyone Had Experience With GFX?

I ended my plumbing career before these gravity film (heat) exchangers came on the scene, so I have not ever installed one: http://www.gfxtechnology.com/VGFX.html

But it interests me because I have a high gallon-per-minute shower in the master bath and a wife that doesn't draw the parallel between the high gas bill with her love of the shower.

I have the height available to install it in the drain line, but do they work?

I saw a TV show on this, maybe Rich Tretheway. Can't remember what the stats were. Seems like a relatively inexpensive device, especially if some rebates are available. So I suspect that there are savings available.

I think it must be installed as close as possible to the shower drain to be effective. Otherwise, a lot of heat is simply lost off the pipes by convection and radiation.