Pros: We enjoyed our stay at Pierre's and he was fast to respond to any questions. The area/street was quiet. The facilities of apartment meant we could cook at home if we wanted, no problem and we could wash our clothes. Good location in the Marais and easy to get around.
Cons: some minor issues. The soda bed was uncomfortable. As a adult you could feel bars in your back through the mattress. The couch itself is very dated and could do with updating to something more comfortable and functional as could the pillows.
Our child could not open the shower door as there is no handle inside if you cannot reach the top of the door to pull open, this could be problematic.
There was a bad drain smell after using the bathroom sink however we found having the exhaust fan up high eliminated this.
If you are tall you have to crouch anytime you are in the main bedroom area, it's only good for sitting/lying or sleeping.
The stairs leading to the loft/main bedroom could be dangerous for small children definitely as a fall hazard. Also the stair landing could take an eye out when walking past.
Lastly there is only a small wardrobe area to unload your clothes, every other shelf/drawer/space was filled with the owners belongings. This made it inconvenient if on an extended stay having to live out of a suitcase for the most part.
I hope the owner can look into remedying some of these issues where possible because otherwise it's a great place and very central. We ended up getting used to all of the above and having a good time in Paris but I thought to give an honest review that these things should be mentioned.