Our stay was really great and Mario was an amazing guest! We arrived very late (around midnight) and he was waiting for us. He also told us about his app, with a suggestion of places to visit and a walking tour: really helpful and well done!
The apartment has been recently restructured and it has all the necessary comforts. It's really close to the metro station with a direct line from the airport, and you can reach the city center by walk in 10-20 min.
I think it's a great place to stay for visiting Porto!