I have stayed in Amstel house for 4 nights in November, and I am really pleased that I have chosen this hostel for my visit to Berlin. In fact, it's their service that persuaded me to stay for two more nights (there was no railway tickets for the most appropriate date, so choosing between earlier and later, I chose later, in order not to miss the walking tour proposed by Amstel house).
They are conveniently located, only 40 minutes on foot from Berlin main railway station, or a couple of minutes from subway station. The neighboorhood is not touristic (which makes possible to find there normal supermarkets etc) but a nice one.
Which was important to me, they are ready to check you in or out any time of day and night (I mean, within the 3 p.m.-11a.m.), as I both arrived and left in the middle of the night, and it was no problem at all.
The staff are really multi-lingual, as I heard somebody speaking, aside from German and English, also Spanish. There're also walking tours provided by a staff member, Fede, (depends on the time of the year, however; I think the one that I took part in was the last this year), which he can do in English, Spanish and/or Italian, and he is really enthusiastic about what he's doing and gave a good picture of Berlin with unusual details as well as showed us where important museums are, so that we could visit them later.
There're also many other activities organised by the hostel, e.g. barbecue parties, and karaoke. There's a wi-fi spot in the reception, but not in the rooms. But there's plenty of place around the reception to sit and catch internet signal.
Despite all those additional activities, the prices are really those of a hostel, and I was pleased with them in comparison with some other 'only sleeping' hostels I visited in other cities.
For additional 5 Euro, you can have a breakfast in hostel, which is convenient and reasonable in comparison with what you can find in the city for this price.
Because I was adding two night of my stay later, I experienced two rooms, of the same type and near-by location, however. There were two 'double-storey' beds (4 people in the room), a big table with a chair for each visitor, and a washstand with a mirror in the room itself. Central heating is powerful, and you can regulate in on your own. There're two wardrobes in the room, by unfortunately there's no lockers so that you can safely put your things there - which is important when you stay with strangers. However, I experienced no trouble with this, those were just theoretical concerns. (There's, however, a storage room where you can put your luggage if you, for example, arrive before the check-in time or leave in the evening of the day you check-out.)
Everybody has a separate keycard, so you don't have to keep in mind who borrows the key first and where to find this person, or to get up to open the room door in the middle of the night.
The only thing I wasn't comfortable with was the shower. However, I experienced only one shower, and perhaps, others are different - there plenty of toilets and showers on the store, so there's never a queue. You can borrow a big towel for 1 Euro at the reception. In shower there's only one premise with no separation of the space where you keep your clothing from where you pour water. Moreover, the shower tap is not convenient, you cannot manage it in order not to pour that water all over the room. It is also advisable to bring slippers if you want to take shower, which I didn't do. However, the fact that I didn't catch a cold with no slippers and no hair-dryer talks in advantage of the hostel's central heating system.
All in all, I really liked it in Amstel house. If I go to Berlin again, I have no doubt where to stay.