It never fails with these tankless water heater threads, the vast majority of comments are from those who have never had one. Opinions are based on misinformation.
We have a Precision Temp unit in our RV. It works extremely well and has proven to use less propane than the tank style units. These units are dependent on water pressure/flow and incoming water temperature. Any tankless system can only raise the water temperature by a certain amount, so if the incoming water is real cold then the max temperature output will suffer some.
These comments are based on actual first hand use.
Keith