I'm not sure why anyone would not be happy with this unit (if it is installed correctly) but I have to say I love it. It was one of the best investments that I ever made for my home!! We have a 2 story 3 bathroom house and it works great for us(4)can take showers 1 after another and there is always hot water. My old 30 gallon tank would have been done after 2 showers. It is not perfect, using the washer or another bathroom can throw of the temp but hey there is always hot water...

After waiting two weeks for delivery, and spending all day with the electrician putting in the correct breakers and wiring, it did not work. I talked to two different representatives at Rheem over two days, and all they could do was send a trouble-shooting guide which instructed checking power to all parts, which the electrician had already done. The return to Amazon was easy and they credited me very quickly (they get 5 stars).