All in all a decent place to stay, absolutely wouldn't recommend to people who are travelling with children as the area seemed awfully unsafe (although I am unfamiliar with the general safety in Paris).
Amenities were poor and only had 6 towels for the 5 of us staying, furnishing quality was also poor as the majority of the apartment is IKEA which I don't expect from an apartment that costs £400 per night.
Air conditioning wasn't working when we were staying although it wasn't desperately needed for us at that time, it did get very stuffy in the downstairs bedroom so they could have used it.
Also the apartment is quite a way away from most major attractions which isn't a problem as you can get to the metro in a couple of minutes however that should reflect in the price of the apartment.
Definitely don't think it is worth the figure.