On the plus side: The reception couldn't have been better, Coro is really very attentive and personable. The appartment has all the necessary amenities, is very clean. Parking is closeby. San Sebastian is not a very big place, so from the appartment (almost-) everything is within walking distance.
On the "not so plus" side: The appartment is located on a T junction with lots of traffic, and there are large garbage bins outside which are seemingly at random collected during the day, at night or in the early morning hours by the local municipality. Even with all windows closed and double glazing it is still noisy.
But all in all we enjoyed our stay. San Sebastian is a nice place to be.