Apart from the check-in, everything was great! It's very close to Haneda and at a very affordable price, so it's a good place to crash if you need to take a flight the next day (which was the case for us).
The check-in works through a tablet which was broken when we tried it. The only provided way to contact support was via phone, which is a problem when you don't have a Japanese SIM. Thankfully some other guests lent us their phone. The staff replies fairly fast on AirBNB as well though! So I wouldn't worry too much about it.