I have been using this (Tempra® 24 Plus) water heater for a week now. I had an American Tankless brand for 6 years before this. I tell you what, the craftsmanship and quality of this unit blows the American Tankless out of the water. I had nothing but problems with the previous unit and that is why I purchased this one. So far I have not had any issues and it produces HOT water ALL the time. It is very user friendly and the temperature is adustable by 1 degree increments, which is amazing in order to get the temperature just right. My previous unit was 5 degree increments and it seemed to be always to hot or to cold.
Originally I did have to have an electrician wire in 3 circuits as inducated in the installation manual. Other than that, this thing took maybe 30 minutes to install, it even fit perfectily to the dimensions I had with the previous tankless water heater.
My only hesitation was that it is made in Germany. After thinking about it, that is probably why it is such a good tankless water heater as this technology has been around forever in Europe. My previous one was made in America as that was one of the main reasons I bought it. Unfortunately, American manufacturer's are a little behind with this technology and it still seems like they are still working the bugs out.