I've had my Rheem natural gas water heater for over 2 years now and can't think of much I dislike about it. Since installation, this water heater has provided steaming-hot water, is very quick to heat up the water, and is fairly economical. The yearly cost to operate is usually much less than $200 which is a big plus and probably less expensive than a comparable electrical water heater. At 40 gallon capacity, the 21V40-38 is perfectly sized for a small family/household, yet large enough to provide adequate water supply..you won't run out of hot water! The water heater functions quietly and has instructions clearly printed on the outside, making lighting the burner a very easy task. This is my first water heater from the brand Rheem, but I would recommend this model and brand to others. The water heater has been free from problems or issues since first being lit and works efficiently in the background to deliver hot water whenever its needed. In the future, I would probably get a slightly more economical model, to reduce impact on the environment, but can not think of anything other than this about the 21V40-38 water heater that I dislike. It is truly a great product.