I stayed in this apartment with other two colleagues, to attend a conference at Palacio da Bolsa. Location-wise, the apt is fantastic: it's literally 2 mins from this well-known attraction, and therefore very close to the Douro river and all the Port wineries.
The apartment has a few shortcomings, however. It is one big apartment that has been created by combining two smaller ones; there are even two separate entries on the stairs. One half of the apt contains living room, a nice kitchen, and a bedroom (close to the main street, so quite noisy). The other contains three relatively quiet bedrooms.
One issue are the bathrooms. There are two, as advertised, kept well-cleaned. However, they are a) interconnected and b) in the middle of the two "apartments". The net effect is that to go from, e.g., a bedroom to the living room or kitchen you have to go through the bathrooms (which may be occupied). This may or may not be a problem depending on how much you stay in the apt; we didn't, so it was not too much of a problem, apart from the need to serialize access to bathrooms/shower, which was exactly what we were hoping to avoid. Also, be aware that in our case one of the two showers had too little pressure and essentially didn't work.
Another problem we had was that the apartment was quite cold. We stay in April, and the weather was particularly bad. However, when we told Cristiano about it after the first uncomfortable night, he immediately provided extra heaters and cranked up the water boiler, so the other days were actually quite comfortable.
Cristiano was also super-nice in allowing me to check-in late (after 1am) on the first night, and has always been very nice and respectful, especially when I reported the problems above.
Overall, considering the location and the nice owner, the apartment is very good; however, despite the fact that it has 4 bedrooms, I would hesitate to recommend it for a high number of people.