I stayed at Joseph's flat in Le Marais for one week and just loved it. The location is so central to everything and you can find all you need food, pharmacy, tobacco/cbd (which is legal again in France) wise within 5 minutes walk in any direction. I experienced amazing weather during my stay and found myself at the river Seine (12 minutes walk) to feel the sunshine reflecting off the water with all of the other young people drinking, eating, reading, etcetera. I will say the studio apartment is just perfect for 1-2 people equipped with a mini fridge, television, full bathroom, two burners, a microwave, all sorts of cooking appliances/useful utensils and micro-washing machine (which worked so much better than I thought it would, really). As well, I was so happy that the location was on the second flight since I was solo traveling with a decent amount of bags...
I will say that with the perfect location comes a lot of city noise, so bring a pair of ear plugs if you are a light sleeper as there was a significant amount of construction echoing from nearby apartments.