We stayed here last week and had a great, if too short a time in Bilbao. The apartment is really well located, with the tram stop to the Guggenheim just at the bottom of the hill and the restaurants in the old town just a couple of minutes walk.
Irene who was looking after the apartment was really helpful, guiding our taxi driver from the airport and booking us another when it came time to leave. We wouldn't hesitate to return to Bilbao and to this apartment.