Customer Rating: - Fresh Hot Water
There is a lot to learn and get use to when you make the transition from a tank type water heater to tank less. I installed it myself. We have a Home Depot which handled the 5 inch double vent pipe. Lowes had all the plumbing fittings missing from Home Depot but no double wall 5 in. vent pipe yet they handle the Bosch line of tank less heaters. It took both stores to find all the parts plus a roofing supply company for the roof penetration collar. It took about 200 $ of parts to install it. I installed it in the same location as my old tank type heater. I knew all of the plumbing would have to be changed which can be done at different times prior to the removal of the old tank heater. You don't want to be left without hot water over night. The general contractor around here can really make your life hell (my wife). The roof vent was a bit of a pain. The main problem is trying to use the existing vent pipe path through the roof (to avoid having a extra hole in the roof) .Enlarging the holes (since old vent system was a smaller diameter) is a pain and clearly point out to me why years ago I should have paid better attention in geometry class. I lived in an 80 year old bungalow I replaced my plumbing with copper pipes a few years ago but mineral build up could be a problem for some people in install.
Unforeseen problems: Low flow plumbing fixtures. All newer fixtures have flow restrictors. If there is any mineral build up it might reduce the flow rate so as it will not trigger the ignition of the heater. Wear in any mixing devices in the fixtures might stop ignition. High temperature supply water. Here in Texas the summer supply water was 90 + you use very little hot water taking a shower causing the heater to cycle on and off. This is where one of the most undesirable issues with a tank less water heater shows up. You are getting hot you adjust the water temperature down and the heater goes off but you don't notice since all the pipes are hot and the temp continues to slowly fall then you notice so you increase the hot flow but all the hot water is gone there are yards of cold water flowing in the pipes toward you . I think there might be a term for this called the cold slug. Cold slug of water. I think the best way is to say the performance of the tank less heater is like a diesel car rather sluggish as compared to a tank type heater which is more the performance turbocharged gas car's brisk acceleration. Another problem I have is my new Kitchen Aid dishwasher will not ignite the heater (to low of a flow rate) but not really a major issue. I live in a old part of town the houses size 80 years ago was around 1000 sq feet now they go to 3k foot easy and a lot more units put in as multiple residents on single family lots . We are using the same gas pipe my forefathers used. So when it gets cold we have low gas pressure. It is getting a lot like a third world county around here nowadays. So lower performance output on those days.
The Plus side of this new contraption. I never will have to use that stale old hot water again only fresh hot water for me. There are only 2 of us living here. I never realized how little hot water we used. We kept 50 gallons ready to go at all times. There was a 300$ tax credit. Fuel prices went nuts this thing will pay for itself probably within 2 years. Actually it cost about the same as the old tank type which I had to replace anyway. When you take in account the tax credit it was basically a no cost upgrade . That general contractor likes to take baths (my wife). It took two tanks with the old heater to get the tub just right. Filling took a long time. One uninterrupted filling now. No more of her camping in the bathroom filling the tub.
Things you might want to consider. They make a larger unit it cost more but it might be worth it for most people. It has a simpler smaller diameter vent which would simplify the install.

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Customer Rating: - Bosch 1600h received with top baffle sections unsecured on one side
Check it when you get it out of the box to ensure the tabs in the top baffle section are all through the front and back plates and are bent over, securing them. When I unpacked my Bosch 1600h tankless water heater I noticed that it was very "flimsy" - after wonder if this thing was just cheaply made, or if I had a real problem, I noticed that the draft diverter section at the top is made up of a number of cascading baffles, each held in place by a several metal tabs that fit through the front and back plate of the water heater, making the unit rigid when they are all in place correctly (and like jelly if they are not). I discovered that all 23 different baffle tabs on one side of the diverter section were out of their corresponding slots on the plate, although the tabs were bent over. Don't know if they all worked their way out during shipping or if this thing was never put together right. At any rate it required quite a bit of dissasembly to remove the entire front plate, bend all the tabs straight, and then some puzzle work to get the straightened tabs on each baffle through the corresponding slot in the plate, and then bend all the tabs over to secure them in place. If I didn't have a good friend who was willing to give up a chunk of his saturday night I would have never been able to make the thing "right".