The apartment is clean and cozy and for us a great location - out of the centre but easily accessible by bus or walking, with a couple of local bars within 5 minutes. Beñat was a great host with a wealth of information about San Sebastian and the local area. Thanks to him, we really got the most out of our few days there.
The only downside for us was that the sound-proofing in the apartment is practically non- existent and we were unlucky in having very noisy neighbours our last night - so bring ear plugs if you are a light sleeper.
Other than that, we would highly recommend staying there.