Vini said on her site it is really important for us to get the best tankless water heater in the market. Because the water heater working for us everyday and most of us doesn't have budget for high maintenance cost.
Reading reviews and pick random product doesn't make you get the quality. Vini marina said you should add your personal factor to get best tankless water heater that fit with your budget and needs. This is crucial, because you will use the device for years.
To get the right item you can take a look at http://vinitankless.biz/ display. They are online reference for this products.