Amazing location. You can walk to anywhere of interest: Notre Dame, the Louvre, the Seine, shopping, restaurants. You can even walk to Champs Elysee, Arc de Triomphe, and the the Eiffel Tower, although that would be farther out.
Alex is an amazing host, responsive, caring, speaks good English, and has everything you need, even plug adapters! The place is clean and very spacious for Paris! I felt like a real Parisienne living here for 5 days.
Regarding the stairs. I recommend everyone ENJOYS the character of going up this old staircase and the charm of living in an of an old Parisian building. And it's great exercise! :)