We had a great time at Osvaldo & Susete's place!
The apartment is really central and it's very close to all the major spots in the city. The area is surrounded by great museums, cafés, and restaurants, and everything you might need is within reach. The neighbourhood might be a bit noisy in the evening, but the apartment is well insulated and quiet. It is also well shaded and cool, so we never had a problem with the heat, even though the temperatures in the city were around 32-35 Celsius when we were there. The apartment is very stylish, and has everything one might need.
Overall, this felt like a top choice in Porto, and we had a great stay at the apartment.