We stayed for two nights at Jovita's place and the location really can't be beaten for this part of Porto - the apartment is right near Sao Bento train station (perfect if you're arriving from another part of Portugal) and the market, shopping street, churches, landmark public buildings, etc, are walkable. The apartment itself is definitely novel in design and it is comfortable, but the space is quite small overall, and we could hear noise from the street below. I would still recommend a stay as it's great value for money and, again, the location was fab!