This is a wonderful apartment in a great area of the city, but it has a few drawbacks. First the great things: If you are looking to stay in Le Marais, you can't beat this location. It is on a quiet side street that is also very close to major shopping roads. You are surrounded by boutiques, restaurants, and shops galore, not to mention the Picasso Museum and the Place des Vosges about five minutes away.
The apartment itself is spotless and roomy. The three bedrooms are each very private, and there are two full baths (actually 4 half-baths, which makes things convenient when you have a lot of people). The living/dining room is bright and stylish with exposed beams and an open kitchen that's stocked with everything you'd need to cook at home.
Now for the drawbacks: The apartment is listed as having air conditioning, and it does--but only in the master bedroom. There are fans in the other bedrooms, but if you are someone who cannot sleep in the heat without a/c and you have your family with you, that will be a challenge.
Also a challenge: the stairs. There are FIVE flights of stairs to get into the apartment, and they are narrow and windy. If you like a workout on your vacation, it's not big deal. But if you arrive with lots of luggage, prepare to sweat. Once you are inside the apartment two of the three bedrooms are also only accessible via stairs, and those staircases are tricky to maneuver as well.
All that said, we had a lovely time in this apartment once we got used it. Veronique and Thierry are wonderful hosts who answered all our questions immediately and could not have been nicer. (I actually feel bad about only giving them 4 stars, but the a/c and the stairs are truly challenging unless you are prepared for them.)