There are two great things about this place. The apartment itself, and J himself. The apartment is quite comfy, and both the bed and the sofa-bed are quite nice to sleep in, providing adequate back support. The apartment building dates back a few centuries and it definitely gives off an authentic Amsterdam vibe. The location is excellent, as well. The apartment is minutes away from Anne Frankhuis, the Jordaan, Dam Square, and the Red Light District, and a short walk away from the Museumplein and Bloemenmarkt. One note of warning though. When packing for J's, do pack light, and do not use especially bulky or cumbersome luggage. The cast iron staircase that runs up the building is exceedingly beautiful, but also quite narrow and curvy. Larger and heavier luggage may be difficult to move upstairs. However, should you find yourself at the bottom of the staircase with no idea how to bring your luggage up, do not worry! We found ourselves in that very position, and J helped us get all the luggage upstairs, which helped a lot considering my mother's bad back.
Which brings me to my second point. J is an excellent host. He was very helpful in all regards, and helped make us feel very welcome. Even before we arrived in Amsterdam, J was a great help. And when our flight was slightly delayed, and we arrived at the apartment a little later than we agreed, J was very pleasant and patient with us.
I could not recommend this apartment and host any more. I would definitely advise you to book J's place (if someone hasn't already beaten you to it!).