This unit competently heats and maintains hot water very well as advertised. However, since the water is heated on demand, it can take much more time for the hot water to get to the faucet than a conventional hot water unit. While the time will vary depending on the distance the water travels, this results in wasting a lot of water waiting for the water to get hot - which adds to utility costs.
Also, if you are looking to save on your gas bill with this unit...you won't. I have used this unit for 8 months (same household conditions before and after) and have seen no significant decline in my gas usage. When you consider the cost of installing this unit against a good quality conventional tank water heater, your payback on a tankless unit is quite long...C.R. says 22 years is the average, but I think that is generous. Also consider that tankless units cost far more to install, as special intake and exhaust venting is required. Rinnai uses an innovative 2 in 1 vent system that works very well, but is very expensive and can add significantly to your overall cost, depending on your particular application.
BOTTOM LINE: I bought this unit since I needed to replace my old tank unit and also needed a hot water heater with a small foot print (due to space limitations. I would add the federal energy credit benefit was a huge incentive...without it,I would not likely have purchased the unit. Therefore, unless you have space limitations and/or can benefit from the energy credit, I suggest looking for a good quality conventional tank hot water heater - the newer units of today are very energy efficient and probably a better choice than the tankless until the technology improves beyond present level.
Review Postscript
I purchased this item through the fulfilling store front vendor listed on the Amazon web-site - I am not listed as a "verified purchaser", since I dealt directly with the plumbing supply house. I needed several additional parts to vent the unit properly. They were a pleasure to work with and provided excellent customer service.