My partner and I stayed in this apartment with our 1 year old for 3 nights.
The information we received before arriving was really helpful and communication with the owners was very easy and prompt. They were more than happy to help with anything we needed and even organised our taxi transfer. We were greeted in person at the apartment which was really nice.
The apartment itself was really well presented and very clean. It had everything we needed for our stay including a high chair and travel cot.
The location in old town was perfect and the views from the apartment were really charming. It's also an easy walk into the more modern part of the city.
Warsaw is a great city to visit although not massively pram friendly! Copernicus science museum is in walking distance and I would highly recommend especially for children.
We would definitely stay here again if we were to visit Warsaw again.