The Location: We loved being close to Gare du Nord, and also the Magenta Station is literally next door. You can access Gare du Nord from there without having to walk outside. It was very very convenient for all our trips around and outside of town - also very convenient to have stores and restaurants that are open 24 hours when you are by the Gare. We found out quickly that Sunday and Mondays are not the best days to find open restaurants in Paris. There are two markets right across the street so you don't have to carry water from far away, but for good cheese, bread, wine, cold cuts, we walked to bigger grocery stores which were only about 10-15 min away. We pretty much walked everywhere from the unit, Louvre took about 30 min Notre Dame about 40 min, Montmarte about 15 min....etc. very walkable. Also the best rates for money exchange was across from the Gare, so that was very convenient as well. Being by the Gare, it's a very mixed crow of passengers, tourists, residents, and those that are trying to make money of tourists, so it's lively and busy at all times.
The Unit: We didn't mind walking up the stairs to the level of the unit, for the most part, the stairs are very wide and easy to walk, last floor up is a little narrow, but even with luggage, it worked out. Neighbors are very friendly, one time when we forgot our keys on the door, a smiling face rang the bell to let us know. There are plenty of windows to air the unit, that was one of the best parts of being on the top floor, to get the fresh air in the unit with Paris rooftop view. The kitchen has everything needed. The full size fridge is very helpful. Living room is very nice sized. The internet worked great. The bedroom was very comfortable. There's sufficient closet space as well. We liked that the toilet was in a different room than the shower/faucet. Made it much easier to share the bathroom. We used the washer once, but it was a life saver.
The Hosts: We briefly met Sebastian during check out, one of their friends helped check us in. We found the host and their friends extremely friendly and good hearted. I'm not sure if they are able to do it every time, but some treats they left for us on the table was an extremely warm welcome, we felt at home right away. Even when they were out of town, Elle and Sebastian were very responsive and helpful. They responded and addressed our requests immediately and favorably.
Overall we liked the location and the unit and of course Paris so much that we extended our trip. Our hosts were welcoming and flexible.