The upside:
Simply amazing location. Right in the heart of Centro but very quiet. There was no street noise (you could hear the local church bells, and New Years Eve you could hear a few fireworks but both were unobtrusive and added to the atmosphere). Host quickly responded to requests and communicated well (including arranging a taxi for our departure).
The downside:
Wifi was not great (no signal in parts of the apartment and very slow where available).
Bit of a sewer smell (heavy rains on our arrival affected the area), particularly the first two days. The host made good efforts to deal with it, but it was there.
The neutral:
There are windows in every room, but they are all on an interior courtyard, two stories below the roofline. In summer this would be great to help deal with the heat, but in winter (we were there for two weeks over Christmas) the lack of sun was noticeable.
Overall:
A great spot, a great value (especially for the location), Seville is not to be missed and this is a good base to do it from.