I stayed in Sofia's place for a 3 day weekend in early August. The apartment is charming, albeit small. Comfortable for 2 people.
The location is great. Walking distance from all the major tourist attractions. I never used the metro. Since I am a runner, I enjoyed that Retiro park was close by for running.
The apartment is located right in Chueca, with lots of bars and restaurants. The neighborhood is lively until the morning hours. The apartment is however not on the street, but on the inner courtyard, noise was not a problem for me. I slept with the windows wide open and it was quiet. I would stay here again.