Marc-André is a responsive and helpful host. He responded to my initial request for booking within a half hour and the whole process worked smoothly.
The apartment is cosy and charming, and set on the 6th floor, above the roofline of most of Paris, offering a great view of a distinctly Parisian scene.
The bed is very comfortable; I slept well. If you are sharing the apartment with others, take quick showers because the hot water water heater is of limited capacity, if you're accustomed to big American water heaters.
If you're returning late to the apartment, know that the hallway lights in the stairwell and hallway are switched off some time after midnight. Be sure to have a flashlight handy, or a cell phone that can be used as one. Also, when you are exiting the building, know that the last door that leads to the street must be unlatched electromagnetically with the "Sortie" button on the wall. This took me a minute to figure out. It may have been mentioned in the welcome message and I just overlooked it, but it's worth repeating.
The area of St Germain des Prés is lively, with lots of cafes nearby. You need only walk a block or two in any direction to find something worth investigating. Metro line 4 is only a couple minutes away by foot, and connects easily to the RER from the airport (the hardest part is navigating the actual Metro and RER stations, which was a bit confusing at first). Additionally, it is easy to reach the Seine and the right bank from the apartment. I reached the Champs-Élysées within a 15 minute walk.
I'd definitely consider staying in St Germain des Prés and Marc-André's apartment again upon my next visit to lovely Paris.