Julia was very welcoming and did a great job as our host. This apartment is very clean and in a very modern building so there are plenty of outlets and plenty of hot water with good pressure. The apartment has lots of windows and a strong fan so it never gets too hot. It's nice that it is all on one floor and is on the first floor (second for Americans) with an elevator but it is easy to take the stairs.
However - it is very small - probably not much bigger than a hotel room and laid out rather awkwardly. Really I can't imagine staying there with more than one other person. The bed is against the wall so one person must climb out of the bed at the end if the other person is in bed. There is a small sofa with a tiny coffee table and no where to sit at a table or use a desk space.
If you are an art lover this is an excellent location - galleries literally next door and across the street. The Marais is my favorite neighborhood in Paris with all of it's clothing boutiques and art galleries. However this is not the best location I have been at in Paris - there are few services on the block - no convenient place to get coffee and the St. Paul Metro is about a ten minute walk.