It will introduce a good bit of moisture into the air in the RV, like a ventless heater. I guess if you're taking a shower that's perhaps not a show-stopper, since showering also introduces a lot of moisture that needs to be vented out anyhow. If you are someplace with cold city water, it would also be rather anemic; you'd have to either have a cool shower or a pretty dribbly one.
I can't tell whether the unit is thermostatically controlled in any way (for varying flow rates). I'd rather hope it would be. It's also not clear how easy or hard it would be to drain for winterizing; pumping antifreeze through should be workable in any case. They didn't seem to have any sort of actual installation or user manual available online; probably you could get one by email for the asking. I wonder what the clearance requirements would be.
