We loved the appartement - it was very well located (just a couple of minutes from the metro, and we walked there from Gare Du Nord in about 20 minutes), and very clean, and stylish and well equipped. It was a great base for seeing the city with our children, and with the windows open in the evening we still felt very much part of Paris with views across the rooftops! Lea was very clear in her communication.
It is worth noting that the apartment is on the fifth floor with no lift, which was fine for us, and quite common for Paris, but might be challenging for others. Also, as it is quite central there is noise from the road in the evening/morning, although again not an issue for us. We would definitely recommend and stay again!