Joel's apartment is in the perfect location, 10 minutes walk to Pont Neuf and Ile de la cité (Sainte Chapelle) and very close to Ile Saint-Louis where you'll find lots of traditional Parisian cafes and bars for breakfast and a late night drink (not tourist traps). Boulevard Saint-Germain in general is great as it has all you need and very cute spots.
The apartment is the perfect size for two, we found it very clean and instructions to reach it were clear. Also the appliances provided were great, and good storage space. We couldn't hear noises from the street (and it's on a pretty busy one) so perfect if you like quiet apartments.
The stairs to the top seems endless the first time but you get used to it, and the view from the flat definitely makes it worthy!! Would 100% recommend.