It isn't worth repeating all of the pro's for this hotel in detail because they are all true:
friendly and helpful staff
good heating in room
But there are a few negatives which I think people need to be aware of although they perhaps wouldn't put everyone off staying here it just would be better to understand what you are getting before you arrive.
We had room 16, a double on the top floor, we knew about the steep stairs and actually we didn't find them as daunting as people had implied. What was a bit disappointing was the size of the room. There was no extra space at all you could just walk around 2 sides of the bed. The shower was a real problem or lack of it. The water pressure was very poor and if someone used the water anywhere else whilst you were in the shower then the temperature kept fluctuating. The other issue was the noise, surprisingly not from inside the hotel but from outside. We didn't know at the time but when we returned home I did a bit of research and it seems that one of the bigger night clubs in Amsterdam - Melkweg is behind the hotel. We think this was the source of the noise until about 2 am on the Friday night and about 5 am on the Saturday night followed by numerous sirens at kicking out time. I accept it is a city and that there is always the potential for noise but it was loud even with the windows closed not sure how bad it would be in the summer if you needed to open them. If you are light sleepers like us you might want to invest in ear plugs.
Having said all that I would thoroughly recommend the hotel overall for it's value for money, location and cleanliness and we did enjoy our stay.