Our stay at Santiago's was absolutely perfect. Although we never met Santiago face-to-face, he was incredibly patient with my many emails/questions before arrival, and even once we got there. He always replied quickly. Since he was unable to let us in due to when we arrived, he sent over his very nice parents to let us in.
The property itself is ideal. Four of stayed in the three bedrooms. Everthing was lovely and we had everything we needed. The location was wonderful: so close to most of the sights we wanted to see, from the beach to an amazing array of restaurants. I would love to move into the place permanently! If I ever go back to San Sebastian, I would stay there!
I suppose the only problem is that, if you have car, parking is either expensive or incovenient, but that would be true any place you stay in central San Sebastian. Everything is in walking distance (or by bus), so if you can avoid it -- don't have a car!