I had a fantastic stay in Valerias apartment. The area is just perfect, if you like urban and trendy and multicultural atmosphere. You will be very quick in Marais and it is just a short walk to the Canal St. Martin. But also right in the neighbourhood, there are fantastic bars and restaurants. Two metro lines will get you easy anywhere you want.
The apartment is well equipped and for parisian standards quite spacious. I stayed there for almost 3 weeks and enjoyed it very much. You can tell, Valeria is a traveller as it is very particular and lovely furnished. I haven't met Valeria, but communication was always easy and Cyrill expected me when I arrived.
Two minor things you might consider: if you are a sensitive sleeper and a quite place is your highest priority, maybe it could be difficult, as you can hear as well the neighbours as also the streetlife and a little bar downstairs (which opens just a few times during the week) - for me that was no problem at all, as i am not very sensitive to noise. Second thing, the matress is not the best, so if you are sensitive to that or have back problems, that could be an issue.
Besides that - totally recommendable!!!! I would definitely stay there again. Thanks a lot Valeria!!