We very much enjoyed our stay in Sérgio's town house. It's lovely decorated, spacious, and all in all a great place to stay when in Porto. We very much enjoyed the fact that it was so close to the metro so getting into town was very convenient.
Communication with Sérgio was great and he was very helpful.
Although we had a great experience, we have a couple of remarks. The stairs to the top floor were a little scary to walk (and very scary to have our child walk) - so perhaps installing a banister would help. We thought the apartment was overall very clean, but the floor was not (downstairs)... so if you like to take off your shoes indoor, you will get dirty feet. While the house is very close to the metro, parts of the neighborhood seemed a little unsafe at night (though in the house, which is walled, you do feel secure).