Our family of 7 (5 adults and 2 teens) spent a week at Haru's place.
Although it's listed as maximum of 10 pax, I think that 7 is just enough, with everyone sleeping in the rooms upstairs. And just enough room to move around the living and dining area when it's time to eat.
Communication before the actual trip was easy as Haru employs the help of a 3rd party team for his hosting services. The support team (and Haru at times) responded quickly to my queries. They provided a helpful manual that included instructions on almost everything - from how to get to the airport to the house, the use of the facilities, English instructions on how to use the appliances (buttons and switches were in Japanese), etc.
Train ride from Haneda Aiport to Keisei-Tateshi station and vice versa was convenient as you don't need to transfer trains (specially if you are hauling around your big luggages).
The place is as advertised - exactly in the pictures. The pictures make it seem larger than actual but space was ok for the 7 of us.
Check-in time is a little late at 4PM but I think this is to give ample time for the cleaner to do his job, which results to a very clean and nice house.
A supermarket is quite near the house, and there are a lot of places to eat around the train station. We tried the Sushi place - it was terrific. It had great reviews on Yelp. We also tried the Tempura place there and got some Yakitoris to eat in the house from there also. All yummy! There are several convenience stores there and even 2 100-Yen stores.
Getting to the tourist destinations from the train station is easy - we usually ended up having to transfer only once. And transfer is easy also.
The house is located in a quiet residential area. Very peaceful neighborhood.
Overall great experience, and highly recommended!