I stayed here alone for 5 nights and had a great time. The location is perfect for walking everywhere, you're very quickly at the top of Montmartre but also southwards. The street is very easy to get to by car or metro and felt safe at night because it's very busy, but no noise from it gets to the apartment at all. It's actually really calm and quiet upstairs, which is great.
The apartment is small but has everything you need without feeling cramped, which I found very impressive. It's nice to have some kitchen amenities and a shower to yourself.
Charlie himself was super welcoming and always really friendly and quick to communicate with. I would definitely stay here again.