I stayed there with two friends a few years ago in a room facing the canal. We all liked it very much. Clean, comfortable, attractive room with good beds. I can only guess that it's a one-star because not all the rooms have baths and because it doesn't have all the luxury amenities that I don't care about anyway.
It has been four years since we stayed in Princenhof Hotel, but it was the 2nd time that we stayed there, as we liked its location, right near a tram stop, withing walking distance of the Amstel and Skinny Bridge, and to Rembrantplein. Probably has 1* as the previous poster said, due to not having W/Cs in all rooms. We did have one with, but it wouldn't have been a problem. The breakfasts were quite adequate and I remember the eggs were topped by a hen egg cosy. Tried to stay there again two years ago, but it was full when we needed it. I'd certainly stay there again.
It is in the Prinsengracht and there is no elevator although they have some sort of pulley system for your luggage. Thanks for everyone's input. I e-mailed them and they returned my post with regrets that they are fully booked for the dates I want in May 2002! Must be popular.