I've had one Rinaii in rent house a couple years ago. I was real unimpressed with it, as in the master bath, you turn on the hot water and then wait a few minutes before you eventually get hot water.
My new house came with a Rinaii, to my surprise (and objection). I think because it's new it may work a little better. It maxes out at 120 degrees, which is something else I don't like.
An upside is, if you have several people in the house, or a lot of hot water usage, then you don't run out of hot water.
They do require occasional cleaning/maintenance, otherwise the heat exchanger can get plugged, which reduces its efficiency.
