I stayed a whole month and I have to say the apartment is great. It's located in a quiet area, within walking distance from supermarkets, shops, restaurant, the City Park, Serralves and the Foz area. It's not exactly in the center, but there are a couple of bus stops in front of the building and there's at least four or five buses to the center.
Filipe was always fast to answer every message. I didn't get to meet him personally, but I met his mother, who was as nice as Filipe and always available. When I arrived, I was greeted with a smile and a bottle of wine. As I stayed for a whole month and wanted to cook at home, Filipe's mother even brought over a couple of oven trays.
The apartment itself is great and has everything you need. There's WiFi, a TV with a lot of channels, a comfortable couch, a big bed and two heaters for those cold nights in Porto. Everyone in the building was extremely nice and polite.
If I had to spend another month in Porto, I would rent Filipe's apartment again.