(Unfortunately it doesn't work well with certain plumbing layouts, and the rising price of copper has reduced the cost effectiveness)
So far so good - we do a bunch of baths/showers at bed time and no one runs out of hot water. Also - I'll add that we accidentally had the plumber remove all the low flow "plugs" from the showers so there's a lot of water flowing.
The pipe is pretty fun - not only is it fun to look at - but when someone is taking a shower it's fun to feel the heat at the top of the pipe and as you move down the pipe it gets colder until it reaches the temp of the cold water coming into the house.
Since it was new construction - we'll never know how much of a different the drainwater heat recovery pipe is making - but it is definitely doing work.
I can imagine these pipes becoming more popular (though rising prices will kill off any efficiencies real fast). Maybe code?
My plumbing layout actually might be darn near ideal for this. I'm not super keen on spending another thousand or so on getting it installed - at least not prior to the "planned but not scheduled" bathroom remodel, but that is at least worth considering when we do do the major remodel and complete bathroom reconfiguration. Our master bath is on the first floor and we don't have a finished basement so making something like this work should be comparatively easy. Thanks for the idea!