I LOVE my Bosch Aquastar 2400ES tankless.
I'm glad you're happy with your Bosch. If you read lots of Bosch reviews, a few things jump out: a) when they work, people are happy b) the defect rate is very high (I found one Amazon reviewer who cited one of their tech lamenting about a 40% defect rate) and c) support is really difficult to deal with.
I'm going to have to replace my Bosch. It is certainly defective. There's a vibration causing a loud noise to come out of the exhaust. I paid a plumber $500 to come out. The Bosch support people had him measure the gas pressure inside the unit with every fixture in the house running full blast -something we never, ever do. I told him that. They didn't care. Lo and behold, the found a way to force the unit into a state where they could refuse to troubleshoot it. Pressure too low they said.
I call out the city. They flow test the meter, and it's fine. A little too high, even, but the tech magnamiously agrees to not adjust it down. I check their WC measurement against the requirements in the installation manual: my gas line is at the high end of their recommend range, but comfortably within it. I also do not have too many fixtures. I call Bosch back, ready to go to war. They won't even talk to me. Literally: they won't even put a tech on the line with me. I am not gas certified. I can call out a plumber again, but it's going to be another $300-$500, and the best I can hope for is service on a unit with a high defect rate. The previous owners of my house actually did all this song and dance once before. The heater is already on its second motherboard. I've gotten a unit with two independent failures before end of life, with many years left to go for more. It probably has a thousand dollars of post-installation labor in it already.
I guess if you're a
gas-certified DIYer and can convince Bosch to talk to you, there's probably a good deal to be had. If not, I think anyone buying one of their units is taking a big risk. Much better to invest in a unit with a lower defect rate.
I have my eye on a Rinnai.