The location is fine if you come and go away with the train (4 mins walk from Sao Bento station), but it would be best to look more into the centre. We didn´t have any problems but didn´t feel very comfortable coming back in the evening because the alley is a bit desolated.
The apartment itself is pretty but we found some hairs under the sink..
The check-in was fine, they have the office of the agency in front of the building and the guy at the reception was very helpful with his suggestions and information about the city. We could also leave our bags there after the check-out and pick them up later