The appartment is very well located and everything is at walking distance. Marja is nice and we appreciated the food and beverages she left for us when we arrived.
Only downside is that the place is very small, mainly the bathroom (toilets are very low, and there is nowhere to put your belongigs or attach your towels). If you are taller than 1.93 expect your head to touch the ceiling. Also as mentioned in other comments the street is loud and the windows are not blocking the sound at all be we didn't bother since we went out a lot (and Marja provided ear plugs).
Overall it's a very good place for the price and the location is simply ideal to discover Amsterdam !