The best thing about Sonia's apartment is by far the location. You can't be more central, 20m from Ponte Luis and within 5-10mins to all landmarks. Bino, Sonia's friendly who takes care of the check-in, was a lovely man, so 5 stars for him. What I really loved too was the possibility to leave the bags in the outside lockers after check-out, how convenient.
The apartment itself was good, kitchen with all appliances, really comfy bed, clean, enough space for one person.
A few things that could be improved: there is barely enough hot water for one shower. I don't know how 2 people would do. There is a weird smell in the flat. For 4-day stay, it would have been nice to get 4 rolls of toilet paper rather than 3, how annoying to have to buy a whole extra pack for one missing roll. And ofc the noise from the street is expected with the location, which I don't mind, but noise isolation with the neighbors is AWFUL. All in all I recommend Sonia's place for a few days in Porto!