The good: it's a pleasant apartment, with large windows looking out to a courtyard, furnished with all the basics one would need. The location is excellent, in a charming and rather quiet neighborhood, and the hustle and bustle of the centric Bolhão is just a 10 minute walk away when you need it.
The bad: the bedroom has no door, which makes for a spacious first impression, but can get quite tricky if you're travelling as a couple and one gets up earlier than the other. The toilet, washbasin and shower are all in the little hallway right outside the bedroom, so a person with a light sleep would easily find the lack of a door inconvenient, as it's hard to flush or wash your teeth without disturbing the other, still sleeping partner.
The house cleaning was flawed.
Communication with the host was really frustrating. They sent a number of pre-scheduled messages (thank you for your reservation, etc.) but failed to reply to any questions throughout most of our interaction, and repeat questions about check-in procedure were met with a template answer talking about the charms of Porto (in 4 languages no less). The host did show signs of life when they (very graciously, all truth be told) allowed us to check in earlier. But for all the rest, our interaction felt robotic, and on various occasions we were left without an answer, automated or otherwise.
In conclusion: it's a very decent place to stay, but it also is an example of what's wrong with a free-for-all Airbnb: a pretty weak hotel experience that's marketed under the pretence of staying at someone else's home.
Would return for the convenience but not for the service.