It was such a pleasure to stay at the apartment! It is really beautiful and authentic and has some old Paris charm (floors, closets in walls, lighting) while all the facilities are absolutely modern and in a perfect state.
It is very spacious, 2 bedrooms, 1 big living room and kitchen with dining table. The apartment has all the utelcies, fully equipped kitchen (though we needed to buy some basics for cooking, like oil and salt, that was just about to finish), TV, iron, a lot of storage space.
Flat was really clean and prepared for our visit, clean towels, beds are made. At the kitchen we found nice touches like coffee capsules and chips.
Hosts were really nice, answered all the questions, Regine met us at the apartment and helped with bringing luggage up, which was very helpful.
Location is obviously perfect, close to Metro, RER (we walked there easily with luggage), surrounded by bars and restaurants, a short walk away from Seine and Notre Dame..
Be aware of the fact it is 2nd floor without elevator (stairs are pretty steep and high).
Regarding the noise: it has 2 bedrooms, one is facing the bar street, that we were aware it could have some noise, another looks at inner buildings and was supposed to be quiet. Eventually both bedrooms had noise, the inner one - starting from 7am it had very loud metal slams, that would mostly end by 8, so it would not be a problem for people who wake up before 7. Maybe it was temporal - from some fixes in the building or maybe it is the noise of the building door, and it happens since people are leaving the building at this time.
Summarizing, apartment is mostly perfect, we enjoyed our stay there a lot, but consider possible noises if you are a sensitive sleeper.