Although I personally did not stay in the space, my sister did, I was in the studio several times. The building is beautiful, the 5 flights of stairs are tough but you get used to them. The studio is lovely, laid out well with everything you could need. It was winter time so we could not make use of the balcony but it was a great space for having a cup of coffee to begin your day or a nice glass of wine at the end of the day.
I will say one thing though, the location, while very close to both Gare de Nord and Gare de L'est, might be better suited for a couple or a single man. As a single woman, my sister felt uncomfortable coming home alone at night as there were always many men (very few if any women) in the vicinity of the flat. Other than that disclaimer, I would heartily recommend the flat!