I recently stayed with Marie for a couple of days in January. Marie was a fantastic host -- kind, helpful, accommodating -- and I enjoyed staying with her immensely. While you don't have the full privacy of your own room, the way that she has a sleeping area set up behind her living room sofa works remarkably well, and the bed is very comfortable. Plus, you have the benefit of walking out the door to find yourself right in the middle of the Marais, just steps away from good shopping, great food, and lots of opportunities for sightseeing that are slightly off of the beaten path (photography museum, Place des Vosges, etc.), where you'll have the sights to yourself if you're there in the middle of the week. It's also a short walk to many of the normal tourist destinations in Paris, and a great location if Notre Dame etc. are on your itinerary.

Marie does smoke cigarettes in the apartment, so if you are offended by smoke then I would recommend that you stay elsewhere. If you're not offended, or can get over it, then you will benefit from an amazingly affordable accommodation in a fantastic neighborhood with a kind and hospitable host.