Great location, good communication with the host. Self-check-in makes it possible to arrive at any time without any extra fee (which is not always the case). Walking distance to most of the attractions in Port, or probably 3 minutes walk to the Metro station that will take you anywhere. I did not try any breakfast place, but there's a big supermarket around the corner. We were able to leave the bags after checking out which was really nice as well. It's a studio, so definitely good for 2 people, but 4 will also fit there (you'll have to pull the straw on who take the main bed :) )
I'd go back to that apartment if visiting Porto again.