We (5 Girls) stayed at Katja's place for a Weekend, the communication beforehand been great, the check-in was excellent, as we were running late and Katja was patiently waiting for us.
The apartment is huge and amazingly located in a safe area in walking distance to many attractions and restaurants, and there is a park in front of it. Katja and her family stayed in the basement apartment, and the kitchen is partially used by her. There is only expensive parking in front of the house, and Katja informed us that there will be free parking only 2km away, unfortunately there is no free parking in Amsterdam City centre, so it was 18 EUR per day. Additionally, there have been a cat in the house we have not been aware of (we had 2 girls with allergies unfortunately), but Katja took the cat into her apartment after we informed her. The actual downside been the heater, it was only 1 degree in Amsterdam and the heater did not function properly, so we ended up quite cold and freezing inside the house. We tried to contact Katja about it, but only received an answer on the next day before we checked out. Besides that, the place is great and highly recommendable for spring and summer time.