My wife and I stayed here 4 nights as part of our honeymoon. The check-in process was clear and easy, and the individual from the Rental agency was very helpful in providing local tips.
The apartment itself was as advertised - very clean, spacious, and comfortable. The location was definitely the high point for us - right in old town, we were always a short walk away from amazing food and both the Concha and Zurriola beaches!
As others have mentioned the place comes fully equipped with appliances, however you need to get things like laundry detergent/pods or coffee pods for the machine yourself. Not a big deal for us - we had a great stay and would recommend to anyone staying in San Sebastian!