This is an interesting apartment, with many pluses and a few minuses. The biggest plus is Ruth, who is an excellent, attentive, communicative and helpful host. The security and electronic access to the apartment are also great. We had a hire car, and secure parking was available. As a base for exploring the surrounds of Donostia (St Jean de Luz, Getaria, Zarautz - all of which I would recommend) it was therefore terrific.
The building itself is not in a very appealing area, as has been said before, but the apartment itself was very clean, comfortable and well equipped. Noise was a bit of a problem (pasing trains, occasional activities outside in the very early morning) but the apartment is equipped with external shutter screens which (once I had found them) significantly improved this. While it is on the train line to Donostia, the last trains were not late, so if one wants to explore the night life of San Sebastian taxi fares can quickly mount up.
Having said all of that, I guess that there is truth in the saying that you get what you pay for. Accommodation in the area is expensive, and this apartment was, in my view fair value. It can comfortable accommodate three or four people