Carlos' place is a great place to stay in Porto. Carlos met us and explained the apartment fixtures and even helped get our bags into the apartment.
The apartment is ideally located in the middle of the historical city. My wife and I agree that we should have book a longer visit. Porto is a gorgeous city and is undergoing a lot of reconstruction. It should only get better looking.
As others have mentioned, the apartment overlooks a square which includes several restaurants so the is some noise. My wife and I are 'city people' and it didn't bother us, but do not expect suburban quiet.
We would definitely book Carlos' apartment again.
Robin & Tom