The apartment is, though plain, very spacious and comfortable. Good bed, very good shower, lots of sockets and storage place.
It is well equipped, except for towels.
The location is perfect: walking distance to everywhere and it is possible to park for free, at 20 meters from the building (Rua do Comercio)
Self checking and check out was perfect as the communication with Joao: almost instant answer and provided every information we needed.
You might have to pay an extra 6 euro per day for heating. We were at the end of April, and the apartment was cold and heating was needed.
We had a perfect 4 day stay in Porto.