Harm's place was perfect for us. The area was close enough to the center that you can walk everywhere while still being away from the madness, there were several good restaurants around as well as a supermarket 5 minutes walking from the apartment.
We only interacted with Harm when we arrived but he provided us with all necessary info and the apartment is well supplied with all necessary appliances, so everything was easy and convenient.
Quick note about the stairs: you will be staying in a traditional Dutch building with limited space. The stairs are narrow and almost as vertical as a ladder, this is how people really live. While we got used to them on the second or third go, if you have joint issues you should maybe avoid this type of building if stairs are usually a problem as there is no lift.
If the stairs don't scare you away, don't go looking any further, this place has it all: privacy, cleanliness, convenience and, I like to think, a taste of authentic Amsterdam life.