The best thing is the location: real, entertaining, multi-ethnic Paris and far, far away from sweaty tourists and screaming tourists kids. It's also right by a metro, a really cool park (running enabled), yummy baguettes and a great butcher.
Unfortunately, the apartment itself has seen better days. While not quite seedy yet, it's on the way and going fast. A bargain at half the price but, as it sits now, not worth it (unless you like mold with your bathrooms).
Also, if you want to park, make sure its nothing bigger than a Fiat 500 otherwise your pride and joy will be leaving Paris with few extra battle scars (unless you are a truly masterful car handler with much patience).