We scheduled our checkin with Philippe (with the agency managing the flat I mean because obviously) and his collegue was 30 minutes late to the checkin. Now, delays happen, workings in the same business myself, I know very well that delays with checkins happen. However you have to let your guest/client know in advance. We have arrived at 11am like scheduled and tried to reach him for 30 minutes by sms/calls until we got an "oups" 30 minutes later.
The person who has arrived didn't even apologize, just stared at us and when we were reluctant he said "are you going to come or not?". Not very friendly, is it?
The place itself is old. It might seem "dirty" to tourists who are not used to Parisian flats but it is actually just really old and ran down. The flat needs renovations, especially the living area. I would suggest that the agency stops the rentals for a while, convinces the owner to renovate the flat and reopen availabilities after that. If not, it will only disappoint further guests.
About cleaning issues, I got in contact with Airbnb directly, on the matter, no need to dwell on that here.