The apartment is great (although a bit smaller then it seems on the pics; but for three it's okay, I wouldn't reccomend it for four persons.
The area of the Marais quarter is phantastic with a lot of good restaurants, Cafés and quite interesting shops. And the main sightseeing points are very near: Just a 10 minute stroll to the Seine, 6 km to the Tour Eiffel (which we did also by walking). 4 km to the Louvre.