The apartment is very bright and spacious and exactly as shown on the pictures. We were just a couple but with the two rooms there is easily enough space for four persons.
The apartment is on the upper floor of the building (4th floor, I think ) and there is no elevator. So keep that in mind if you have heavy luggage.
We got the keys from the concierge service without any problems and the communication with Catharina was really good.
The location of the apartment is a good starting point if you want to explore the city walking and doing some sightseeing. We had a wonderful time at Catharinas apartment.