Alix made the check-in very easy, even after our train was delayed.
The flat itself is very decorated and well equipped for 1-2 kids with a bunk bed and toys. It's worth noting that the house suffers from thin walls so that you can hear the neighbors above walking their hardwood floors. Because of the traffic noise and smoke from a bakery/coffee shop below you can also hardly open the windows.
Also, the tap water tastes a bit too much like Chlorine. Not anyone's fault but better plan to buy extra bottled water.
Nevertheless, the location of the flat is really good. You've got access to several metro lines, a tram line and busses. A supermarket, several bakeries and a really lovely park are in walking distance - you'll easily reach every place in Paris.
Overall it was a great pick for our base camp for a week in Paris with kids.