We just had a short stay, and this apartment is located in an area that is convenient to Gare du Nord, Gare de l'Est and Metro Line 4 that's only a few stops from Gard du Nord. The bed is comfortable, heat works well (floors are cold in the winter) and the kitchen is very good for its size. Communication was very good with the owners too.
There is plenty of nightlife in the area as well as interesting restaurants to dine at. I recommend it for those who are one or a couple. Prices are a bit high for what you get, but it's Paris.