All in all our stay at the apartment was really nice. The location is good - I wouldn't recommend going everything by foot though, as it can be quite far. But there is a bus station right in front of the door, so you can reach everything with the bus/metro (city centre, Vila Nova de Gaia, beach, train station, airport,...).
There is also a supermarket (Lidl) just about 5 to 10 minutes by foot from the apartment.
We enjoyed our stay here and would recommend it for city trips to Porto :)