I was very satisfied with my stay at Room 23. There was no problem with checking-in later (you just need to call in advance to let them know) and the hotel staff was very polite, helpful and attentive. They even allowed me to put a few things in their small personal fridge. The room was on the top floor, no elevator, but it was kind of nice. I was really glad to have a room with a toilette and a (really) small sink - it was very convenient and I don't think I'd stay in a room without it. I did not mind common showers (there are two) as they were clean. I stayed in the hotel in May, so it was hot and no heating necessary so I can't say how it'd be in the winter although there is a radiator. The only small thing that could be better was wifi - very slow. But as I was out in Paris most of the time, I did not mind. I do recommend this highly if you don't want to spend too much money on accomodation - it's great for the price. And the area is proper, I recommend Au Pays Natal and Doppio for food near the hotel (serbian and italian). The connection from Simplon is also good, close to the hotel. And I think most people in Paris have to travel around 30 min to get somewhere anyway. And it's not far from Sacre Coeur by foot, around 20 min and you get there from the other side and stroll through the lovely streets - be prepared for stairs, but it's charming.