They are common in other parts of the world. They don't take as many long hot showers or fill whirlpools anywhere as often, either .
Often, in order to ensure it can raise the temp, they install a flow restrictor. The water can't go through the thing "too fast", or it doesn't have enough time to heat, thus the restrictor. While they don't take much of any power while idle (maybe a few watts in standby), they take significant energy when running. If electric, expect to possibly have to upgrade your service (maybe not, but don't be surprised). If gas, you'll want to probably direct vent it to the outside for intake and exhaust, or you will need a quite large area to ensure you have enough combustion air.
If you live where the incoming source water is below 50 degrees (how most of them are spec'ed for output), then it may not reach the desired temperature and volume. Last winter, my incoming water was in the low 30's, yours could easily differ significantly. If the anticipated use is within the units capabilities, it will probably work out. Just make sure you read and understand the specs and know what you really need it to do. Take into account the quantity of fixtures you anticipate running at any one time, and either live with the flow, or buy a bigger one, or accept that the water doesn't get as hot.