Can't recommend highly enough! This was the best place we stayed in during our long road trip. Incredibly cozy and well designed apartment. The bed was really comfortable, which is important while traveling, but surprisingly hard to find! Great location, just a 5 minute walk to the Old Town (Casco Viejo) and to the city center. No AC, but there was a fan, which was enough to keep us comfortably cool at night in August. It's also a quiet neighborhood, so we kept the windows open, which helped.
Hosts were very communicative and gave very detailed instructions (a bit too much in my opinion, but that's personal preference). They take hosting very seriously, so rest assured that any question or need you have will be addressed promptly and kindly! We plan to come back to Bilbao and would definitely stay here again!