We had a lovely stay in Ana's apartment. She is a very friendly owner, flexible and willing to help out with anything. The apartment is in the middle of the center, next to the Praca Liberdade, which is very convenient because everything is on a walking distance. The main train station takes a 5 minutes walk. On the Praca Liberdade one can take the bus to the beach which takes approx. 10 minutes.
The apartment itself is very clean, spacious and on the balcony it is perfect to have breakfast or a drink. The kitchen is provided with all the stuff you need to cook your meal and the supermarket is around the corner. The bedroom is spacious as well, the bed is really nice and the only downside of the bedroom is that is located at the street side. This means that during the night it can be a little bit noisy, but nonetheless we had good nights.
I would really recommend this place to anyone visiting Porto.