We stayed with Christian for eight nights just before Christmas and had a wonderful experience. The apartment is very intelligently laid out so you never feel cramped and there is a place for everything. The bed was very comfortable and it was plenty big enough for two tall adults. It is a quiet place and there was never any problem with noise stopping us from getting to sleep at night.
It is easy to get around Paris from Christian's place as the Metro stop is literally right around the corner and there is only one change to get to the RER that takes you to and from CDG airport. There are also lots of excellent cafés, bistros and other shops within easy walking distance, not to mention many museums and tourist sights.
Christian himself was incredibly friendly and helpful. He was very welcoming on our arrival and easy to contact and ready to help if we had any problems.
We will definitely try and stay at Christian's apartment the next time we come to Paris.