A nice apartment in a relatively central area. You can comfortably walk to a lot of different and interesting places. The apartment itself is nice, the only complaint I would have is with the kitchen. I stayed for a week and saw roaches running around in the cabinets and kitchen counters about 4 or 5 times. I think the roach problem is due to the fact that the building is old. The owner of the apartment keeps it clean, and there are no messes that would attract roaches, yet they are there for some reason.
Aside from the odd cockroach, everything else was great. The host was very accommodating, communicated well, and wanted to make sure I was getting the most out of the city. Outside of the kitchen, the apartment was very clean and well decorated.
The Retiro neighborhood streets get very empty at night. You should be cautious when going out at night, not taking valuables with you just to stay on the safe side. I ran in to some weird characters while walking around at night. Trust your gut. Also be very careful with your belongings at the Retiro bus station area, I had someone try to steal from my backpack in the middle of the day in the crowd.
All things considered, this apartment is a decent stay if you want a place to yourself in a centralized place in the city.