We just returned from our 7 day stay at the 5th Heaven. Cristina and Mateo are extremely attentive hosts. The apartment is exactly as described. The location is perfect. It is close to metro stations, shops, cafes, markets and a laundry mat. We felt safe walking everywhere even at late hours. It was very simple to get to the apartment from CDG by train following Cristina's instructions.
The space, although small was clean, neat, and had pretty much everything we needed. A small fridge, a microwave, a small shower with hot water and a sink. The bathroom is a little odd for the American standards...but we were happy to not have to share a bathroom while vacationing in Europe :)
The bed is two twin mattresses backed together that gets set as a couch for during the day. The pillows and the duvet provided were nice.
The apartment sits on the 6th floor. Great view of the street and other building rooftops. Climbing up the stairs was never an issue for us.
Overall we loved and enjoyed our stay very much. We recommend the 5th heaven if you are okay living small while you travel...the location of this place makes everything worth it.