Sophie's apartment is in a dream location in Le Marais, within walking distance to everything my friends and I wanted to see in Paris but on a street that always felt very safe. The apartment itself was fabulous - the only downside is that you do have to go up a fair number of stairs to get to it. She includes a guide (in 4 languages) to the apartment itself, so it's super easy to settle in once you arrive.
Sophie herself was wonderful; she responded very promptly to every message I sent, and went out of her way to ensure that I knew about anything that could potentially make my trip inconvenient (e.g. the daylight savings time change that occurred the morning of my flight home). She clearly cares very deeply about the well-being of her guests.