We were really happy with Ricarda's place. As the description states, it is a five-floor climb up to the apartment but its not a big deal. The apartment is spacious and even in the cold winter (we visited in December), we were still able to take advantage of the huge terrace on the roof. The apartment has plenty of heaters. The apartment is also perfectly situated -- the closest metro stop is a few blocks away and many great Parisian landmarks are a quick walk away. It is also in the heart of St. Germain and right above a handful of great restaurants and bars. It is worth noting that because of the restaurants and bars below the apartment, people tend to hang out in the streets late into the night (like 3-4am) and there was a bit of noise that could be heard from within the apartment. This wasn't an issue for us but may be some folks looking for complete silence at night.
Ricarda gave us a bunch of great recommendations when we arrived. We also happened to be there during a country-wide strike which had a significant effect on public transportation. Our hosts were thoughtful enough to reach out prior to our arrival to give us a few tips on transportation from the airport. We would definitely stay here again.