We had a wonderful time in San Sebastian, and this apartment was extremely well placed to see everything (and just 5 mins from where you are dropped from the DO50B bus that brings you from Bilbao Airport). The Old Town is just over the bridge and we felt like we were in the middle of everything without the night time noise of being in the Old Town itself. The room itself was big and had a very comfortable double bed, plenty of cupboard space some chairs a TV and a fan (which was needed in the heat).
The private bathroom was across a communal hallway (i.e., not an en suite), and was well kitted out including a very good shower (water pressure, heat etc.).
Everything was sparklingly clean when we arrived, and the hosts Michel and Theresa were very courteous and responded very quickly to our messages before and during our stay.
Note that there is no kitchen, but the tap water in the bathroom is drinkable and there is a coffee / tea station in the communal area (long life milk - no fridge). Also, it's worth noting that when we stayed in September 2019 there was scaffolding on the building so the balcony was less appealing - although given how much is going on nearby we wouldn't have had time to use it anyway.
Overall, we had a wonderful time and considered it good value for money in September (a great month to visit the city as it's still warm but less busy / expensive than July / August).