The location here is amazing - a tiny, pedestrian-only street in a great neighborhood that is just a 10-min walk from the major sights, but also far enough away from things that it's not touristy. The apartment is inside a secure building, overlooking a quiet courtyard. Very peaceful. It was cold and rainy when we visited, so we did not explore the roof area that other reviewers have raved about.
Sergio is a great host - very friendly, timely communication, enthusiastic welcome. He let us check in early, and he provided us with a detailed overview of the city with spot-on recommendations for food, flamenco, etc. We were there for 4 cold, rainy days in March, and Sergio thoughtfully left us a giant umbrella, which was much better than the dinky one we had optimistically brought. Much appreciated!
I am giving four stars because of a few issues with cleanliness. The shower curtain was a bit mildewed, and there was an unpleasant odor in the bathroom. (Again: it was very rainy when we visited, so this might be related to the general lack of circulation in this older apartment.) Our towels began to smell musty after two days too, despite our best efforts to dry them. There were no backup towels to switch to.
In the kitchen, the fridge smelled a bit stale, and we weren't entirely sure about the cleanliness of the dishes - we felt we needed to wash them before using just to be sure. When I used the washing machine, a mosquito flew out and bothered us for the next three days. There seems to be some standing water permanently caught in the lip of the front seal of the washer.
Hopefully these are all "rainy weather problems". I'll say again that Sergio was very nice, very communicative, and that the apartment was very quiet and in a great location. Overall we had a nice stay.