We just returned from a weeklong stay in David's apartment in Le Marais. It was a great choice for our family of four, as the two bedrooms provided ample space for two adults and two children. The kitchen, while small, never left us lacking for anything and we even cooked a few meals at the apartment. The WC and the washroom were separate, which - while typical - took some getting used to but was not a big deal. The living room was very comfortable with a huge window looking out on the neighborhood below.
Speaking of the neighborhood -- this is where the apartment earned five stars for us. The apartment is on a small side street just steps from Rue de Bretagne, which is a lovely and very useful high street with everything you need -- restaurants, cafes, wine stores, groceries, patisseries, a pharmacy -- and allows you to assume the life of a real Parisian. We spent lots of time just exploring the small streets of the neighborhood and didn't run into a lot of tourists -- which is how we like it! The real highlight for us was the lovely park just three blocks away, which was the perfect spot for our children to mingle with locals at the start and end of each day.
The apartment was also an easy walk to several different lines on the Metro, which we used frequently to explore other areas of the city. Overall, we were very happy with the location of this apartment and felt like we couldn't have made a better choice for a family visit to Paris.