It's a wonderful apartment, right in the old city, in fact the pictures don't do justice to the apartment. The tower of clerigos is visible from the windows! It's near university area, lots of bars and places to eat, the Sao bento station is 5minutes away and the famous tram22 passes right under the apartment window. Plus, a taxi stand - across the road...
Couple of things about the apartment -
1) very comfortable for 2-3 people
2) claudia, our host was extremely prompt with all our questions
3) the apartment has all the works that one would need for a comfortable stay
4) It's a small place, so avoid carrying heavy luggage plus there's no elevator so you would need to carry them up and down on your own
5) it will be nice if there are some small snacks like jam, butter, a loaf of bread or something left in the kitchen. We reached quite late in the evening and would have liked to grab a bite considering most places were shut by the time we got to the house. However in checking the kitchen, we could only find a used pack of coffee.. this however is just feedback, for those reaching early, there is a cafe right under the house :)
All in all, a great stay and we had a wonderful time in beautiful Porto.