The apartment is perfect for couples looking for a place in Porto near the subway and at walking distance from several Porto historic sites, including São Bento station, which you might include in your tour if you want to visit other cities like Braga or Guimarães.
Joana, the host's mother, met us with the keys and kindly talked about the surroundings. There were fruits and wine waiting for us.
I recommend Paulo's place. Just keep in mind that due to the glass walls you may end up waking up your partner at night if you turn on the lights in order to use the bathroom. And be careful with the kitchen's water tap, which is a little bit tricky to control. Other than that, it is an adorable place.