If you're expecting to have large baggage, the stairs might be difficult to walk up (the unit is on the 4th floor). The stairs are steep and narrow.
The bathroom is extremely small. I think most people need to sit on the toilet sideways if they choose to use it with the door closed. There weren't many basic toiletries (no hand soap, limited paper towels & toilet paper, shampoo/conditioner).
The unit is on a nice, quiet street yet close to restaurants and attractions (Louvre and Notre Dame, specifically). My wife and I even walked to the Eiffel Tower, but that was a long walk!