Great experience, would definitely recommend!

* Clean
* Quiet - All windows open to the inside courtyard, not the busy and loud street.
* Can be completely dark for sleeping - Windows have shutters
* Secure - Outer door w/ keypad, inner door w/ keypad, three bolts on door
* Great location - Easy walk to Gare du Nord, can see Gare de l'Est from end of street. Grocery store is close by
* Fully stocked - Kitchen, bathroom, AC power adapters
* Good WiFi - 11mbps down, 1 up, ~28ms ping.
* Nice shower - Clean, good amount of room, good pressure. Water temperature can wander a bit, though. I think it is due to being on the top floor in an older building, with an older on-demand gas heater. But, carefully set it in the middle of your temperature range to start, make very small adjustments, and you'll be fine.
* Great view!
* Comfortable bed
* Towels were nice and clean, and smelled good
* Spiral stair case is rather tight. Nothing negative against the apartment, Sonia says in the description that there is no elevator, but I would caution those that have health considerations that would affect their ability to get themselves and luggage to the apartment.
* The windows open out to the side, and can lean back at the top. Very cool!
* Can get hot - Seems like air conditioning is a rarity for Parisian apartments on AirBnB or VRBO, so its not like Sonia's place is out of the ordinary in not having it. But, since there is no way to get a cross breeze, it can get pretty warm. We were there on days in the low to mid 80s (F), and while it was comfortable enough while awake, it was warmer than I prefer for sleeping. Being that I also prefer it dark, I had to chose between whatever air I could get through the open windows, or darkness. HOWEVER, it was not so warm that I couldn't get to sleep. I wouldn't let it discourage someone from staying there.
* It appears that somebody may live here some of the time. Not a problem, but just know that the freezer is already most of the way full and various storage pieces have stuff in them.

Overall, I'd say it was an elevator and air conditioner short of perfect. But, neither of those items are a big deal, and both are mentioned in the apartment description. The only surprises were pleasant ones, and it was a very positive experience. I recommend it without reservation, and should we come back to Paris I highly doubt we will be looking for a different place to stay.