We had a lovely stay at Gisela's apartment. Location is in a lively neighborhood with lots of restaurants, bars and shops. Also close to the metro and places of interest.
We stayed in the apartment with our 3 year old daughter. The apartment was quiet and kid-friendly (she slept on the sofa-bed) although you have to be careful with the balcony.
We would recommend Gisela's apartment to friends who are going to visit Porto