I booked this for my partners birthday plus an additional guest (my brother in law) for a 3 night stay.
unfortunately a couple of days before our flight we were informed of a maintenance issue, and therefore an alternative property of was offered.
Given our time constraints we accepted this as we didn't have time to look elsewhere and everything was already booked and paid for.
Here is a link to the property we stayed in:
https://pt.airbnb.com/rooms/25282120?guests=1&adults=1
Firstly the good points of our alternative accommodation:
It was tidy and ideally located to walk into town, the lady who greeted us was polite and showed up promptly for our arrival and the customer service team was helpful.
Our negatives would be:
Our initial booking was for a two bedroom apartment - our altnerative apartment is a one bedroom with another sleeping area directly outside the main bedroom with no privacy.
90% of the time there was little or no WiFi signal, and there was no proper kettle.
Overal the alternative apartment we were given is not bad, however our expectations were not met as we paid (the same price) for a higher spec apartment, with two seperate bedrooms, balcony with seats and tables, nicer decor and better equipt kitchen, and just as centrally located - and feel that the property that we stayed in was not of the similar level.
Please see links to compare for yourself.

Porto itself is very lovely and fairly easy to walk about once you have got your bearings.
The metro is easy to use and is a great way to get around quickly.
A particular highlight was the Crystal Palace Park which views a cross the city and river are very beautiful.