The pros:
1. Lovely apartment, clean, as pictured, etc.
2. Very central, great location
3. Responsive hosts
The cons:
1. Rules are a little draconian (e.g. no music, no guests who haven't submitted ID cards?), although I'm not sure how enforced they are.
2. There's a significant deposit outside the airBnB platform that you have to go through to get access to the flat. That wasn't something I was expecting, and makes the rules more scary.
3. Flat is quite noisy (internally, you can't move without another guest hearing) - although I guess that's true of a lot of Parisian apartments.
4. To get into the flat, you have to access two lock-boxes, one of which is a couple of minutes from the apartment. This was very odd to me and didn't really make sense.
5. For an apartment hosting up to 10 people, providing only one key was a really strange decision.