The apartment is wonderful. The apartment is clean, well appointed (you can tell the owners have a good sense of design) and close to the train stations, which was very convenient for us given we came to Paris on the Eurostar from London and left on the high speed rail for Amsterdam from Gare du Nord. The metro was also conveniently located just 1-block from the front door, which made heading into the city to see the sights quick and convenient. The outdoor area of the apartment was particularly wonderful for relaxing after a long day of sightseeing with a glass of Bordeaux under the shadow of a gothic cathedral. The ambiance is hard to beat, anywhere.
This apartment is a really good value for your money.
That said, the neighborhood was a bit more than "colorful" (we witnessed two fights nearby during our stay), and although I was comfortable with the surroundings as a seasoned traveller, my mother and sister were very apprehensive about leaving the apartment without a male companion. If you're adventurous this shouldn't be an issue, but less intrepid travelers may want to consider staying further away from the train stations and a tad closer to the downtown sights.