Our Trinity 150c (hot water combo) replaced a 1940 cast iron boiler and rental hot water heater in fall 2007, six years ago. The gas usage went significantly down as expected, and our comfort went up because of the boiler's ability to modulate its burn rate to a lower rate when the outside temperature is warmer. We reclaimed floor space too. For a 1300 sq. ft household of two, the on-demand hot water works perfectly, capable of supplying adequate hot water for a shower and appliance or two (e.g.dishwasher, washer) concurrently without slowing down, even sourced with icy Ottawa water in winter. The boiler was recently opened and cleaned for the first time and needed almost no cleaning after six years. (Manufacturer states that unit should be cleaned and inspected after first year, as usage and local conditions may vary.) The only failures in six years were not the boiler itself. The external Watts overpressure valve started leaking this year and needed to be replaced. I see Watts now have an M2 version, so perhaps they have resolved a problem with the M1. Also, the secondary (radiator) loop pump was replaced twice under warranty since installation, but I blame the pump manufacturer Bell and Gossett for that quality, not NTI. I replaced the B&G with a Grundfos pump that does the same job, and is virtually silent and only uses 23W of electricity. NTI has all their installation and technical manuals on their website. I encourage anyone who is at all technically inclined to download and read the manual before purchase as I did, and keep an eye on your installer and installation. Ours did a messy job overall, but at least followed NTIs instructions properly because they had no experience when they did our installation. I recommend this model based on my experience.