I wouldn't describe this apartment as particularly nice or comfortable but it did the job. It very clearly needed a deep clean but it wasn't dirty either.
I had a pretty big issue with check-in. I asked for instructions at 7:30am to give them plenty of time to respond as check-in was at 3pm, ended up messaging multiple times, and didn't hear from them until 6:30pm. They were apologetic for the tardiness but it doesn't make for a very good experience. The apartment is in a busy area and most travelers will have luggage with them.
The tldr here is: it's close to Gare du Nord which makes it convenient for a first or last night of a trip but personally I wouldn't want to stay longer, and just to be safe make sure you get check in instructions ahead of time.