We stayed for 5 days/4nights here and it was a great experience. The apartment is very nice and cosy, very well equipped. The bed (sofa) from the second bedroom was very comfortable, so don't worry, you will sleep well.
We really enjoyed staying here as the apartment is close to center (15 min by bike). Also, our guest, Jeroen, was very nice and friendly, he made sure we had a great stay.
I recommend Jeroen's apartment and if we ever come to Amsterdam again, we would definitely stay here.