The apt is very well located (!) - close to Luxemburg garden, Pantheon, and the downtown. The street itself is very lively, with lots of bars, cafes and restaurants.
Martial is a great host - easy to reach and fast to reply to his guests' messages.
At the arrival we got stuck at the airport for longer than expected, so we couldn't meet Martial in time. He arranged everything, so that we got the keys fast upon our arrival. He and his girlfriend left maps with marked locations of the closest supermarkets, metro stations, etc. They also left some little things for breakfast, which was very nice of them, and made it feel at home.
In a word, Martial is a very nice host, and I would recommend staying at his apt for 1 or 2 people. One small thing that bothered me - noise from the yard when cafe's employees started their work in the morning.