Odet's apartment is exactly what it says in the description. The apartment on the inside is beautiful and laden with a special artistic sense form the host. The place had everything I needed, and the grocery store is literally downstairs (incase you plan to cook). The building itself is slightly run down, but I guess it is to be expected from old buildings of Paris. Also, it looked like repairs were underway and maybe within a few months the place will be as good as new.
It is located in the heart of the city. The 5 days that I stayed there, I walked to all the places in Paris (as far a Luxembourg gardens). This included returning as late as 4am a few nights. The streets near the apartment can seem to be slightly seedy very late at night (after 1am when bars are starting to close), but I was not bothered by anyone and didn't feel particularly unsafe. Also, if you are not one for walking then the metro station is less than 2mins walk.
There are some great bars and restaurants on the street where the apartment is located (I would recommend checking out Pardo or the little alley way with all the indian restaurants), I would often stop there for a drink at the end of the night. They are very lively and full of young people. The place is perfect if you like meeting people and having a good time. However, the presence of bars does mean that the street can get noisy and stay noisy till early hours in the morning. Closing the windows can alleviate this issue, as the windows were almost sound proof, but maybe you don't want to do this on a hot day.
If I was to personally visit Paris again, I would probably try to reserve this location again.