We used Paris Attitude to book an apartment for my in-laws last March. It wasn't the greatest experience. What we found frustrating was that the price quoted on the website and in our first communications with the agency was very different from the actual total price. After cleaning fees, mandatory rental insurance, and other administrative add-ons (which were not listed on the website or in our first emails with the agency), we ended up paying double the price we originally thought the apartment would be. If you decide to use this agency, just beware that the price you see on the website is not the price you will actually pay, and don't sign any agreements until they have quoted you the total price with all fees included.
On the positive side, the apartment was safe, clean, and comfortable, and communication with the agency was always prompt. My in-laws said the check-in and check-out process went fine, too. We just felt like they could have been more up-front about the fees and insurance.