Martijn is super nice, and so is his apartment! Martijn helped us navigate the public transport to get from the train station to the apartment. It is near Fredrik-Hendrik place, which has a nice children's park, and several bus and tram stops. It was very easy to get around Amsterdam using the trams.
At the park, there is Cafe Broer, which Martijn recommended to us upon our arrival (totally jet-lagged from our overnight flight), and that was perfect.
There are several flights of stairs from the street to the apartment, and the steps are very shallow and flights very steep -- no problem for our family whatsoever, but Americans may find them surprising.
The bedrooms are lovely, the bathroom is super modern, the shower is great. Europe was in an extreme cold spell when we were there, and the apartment was warm and cozy, flooded with sun in the afternoon.