Bought one during fair, used for about a month, so far so good, satisfied.

1) With temperature set to a fix value, the power applied to the water heater depends on the incoming water flow rate, example, if water flow rate suddenly lowered, the power applied to the water heater will be lower also, hence reduce power consumption, and vice versa.

2) Water pump is always turned on whenever the unit is turned on via the push On-Off button, no way to turn off the pump manually. The pump noise level is acceptable for me, not too loud.

3) Water temperature settings retains as long as you don't turn off the main power supply to the unit. The clock settings will always get retained, regardless of the main supply, because there is a coin battery inside the unit.

For me, the water pressure coming out from the Panasonic DH-3NDP1MS water heater is just nice.
Staying in around the middle floor of a 29 floors condo.

My preference towards not so powerful water pressure as I do have experience using water heater with high pressure water that feel hurt on my skin during showering.

I believe this water heater can vary its pump speed according to the incoming water pressure, to maintain steady water pressure or flow and also water temperature.