The apartment itself is beautiful, and Claudia (the host) was extremely friendly and helpful - offering many tips on what to visit in Porto and responding quickly to any questions I had. Location wise this is also in a brilliant part of central Porto...but there is one quite big drawback.
Right now, there is a very large building project going on right near the apartment - and so there is loud drilling and hammering throughout the day. This is not the fault of the hosts and so I feel bad not giving 5*, but for me, this was the one frustrating part of an otherwise fantastic stay at a stylish, spacious and convenient apartment.