Would definitely stay again!
Siestal is just 5 mins walk from Okachimachi station (closest to Ueno, one of very big stations, truly convenient). If you want to, you can even walk from Akihabara to Siestal in 15 mins!
Just, host and staff don't speak English. But they use a translator device, which is okay then.
There were not many people staying when I was there, only around 4-5 each floor. But it's always quiet and available for any use of bathroom or toilet. Everything is clean and convenient. They even offer free boiled eggs in the morning!
The house is not big but it has got lift inside, so if you have bulky luggage, not a problem! With this vale rent, it's a perfect place for solo travellers or groups!