Well, first of all you have to consider that Amsterdam is a hell of an expensive city! In fact you can see that this "private room" seems to cost almost like normal "hotel rooms".
However, you have to consider that it is indeed a "mini-private apartment", since the entrance is totally independent from Bart! Then the position, which is really great, being few minutes away from Damsplatz.
Lastly, the apartment is really small, but pretty well organised! The bed is comfortable for 2, and the toilet even if tiny has everything you need.
Oh, lastly, remember that there is no elevator, so you have to bring your luggage with you for 3 steep stairs! But again this is almost normal in Amsterdam city center.
In the end: super positive experience!