We stayed at Mario's Boat in September for 5 Nights. It was much more comfortable than I dared to hope it could be on a houseboat. But it is such a cozy and scenic place to stay!
Water, electricity, TV, the coffee maker, everything was alright and worked perfectly. We greatly enjoyed the nice location/area, as almost everything in (central) Amsterdam is in walking distance and there are a lot of restaurants in the area.
Contact with Mario and his Co-Host was without problems as well.