I traveled to Amsterdam with my wife with a specific purpose. We needed to stay close by RAI, and the apparent perfectly matched this criteria.
Janet and her husband are very helpful and respond quickly to requests such as (need to heat up food in a microwave, need to iron clothes, need help with heavy luggage, need to buy specific items, need to find a good restaurant).
There are only a few potential drawbacks to consider: If you travel during winter time, as we did, it may be a little cold in the room. I would recommend this apartment for younger people, but if one has issues climbing up to the 4th floor, I would consider another option.
In our situation the advantages outweighed the disadvantages, so we were happy with the reservation.