We loved our stay at Ludovic's appartement. It is in a lively, multicultural neighbourhood, though we were amazed at how soundproof the windows were. But - as you can expect in a big city - you can still hear some noise at night. The location is great: 15 mins walk from the Thalys, 15 mins to Montmartre neighbourhood, next to a metro so you can reach the Isle de la Cité quickly.
Most importantly Ludovic is very kind and accomodating, and tries his best to help you out. He has a wonderful personal style which you can feel throughout the appartement, resulting in a feeling of coming home inbetween your Paris adventures. Me and my friends would definitely come back!