We had a great stay in Amsterdam and the apartment was one of the many reasons. It's spacious, has good natural lighting, and is located close to important amenities (3min from a supermarket, for example). The fact that it is 420 friendly is also a big +.
The stairs are quite steep and there are a lot of them to climb before getting to the apartment, but I feel that this would be the case with almost any apartment in Amsterdam.
Nike was great, she was flexible for our check-in and check-out hours, and was always quick to respond.