We have a Takagi Jr heating our shop floor at the farm for at least 12 years and never had an issue with it. Building is 60x80 and once concrete is warm it hardly runs. I am pretty sure someone bought Takagi.
I am single and got tired of the hot water heater rotting out and put in an A.O. Smith on demand with propane. That was about 5 years ago and never had any issues with it. Even had a hot water tank go bad under warranty and the installer would have had to order one and I would have had to pay shipping. That was about as high as just getting a new one.