I came to stay here with my girlfriend for 4 nights in June.
The check-in was very smooth - the hosts were very flexible about timing and we were welcomed at the door before being given a very useful collection of tips for the local area. Throughout our stay the hosts were very prompt with any communications.
The flat itself was very clean and well stocked with all the necessities. It felt spacious and light inside, and the whole interior of the building looks like it was renovated fairly recently. The bottle of wine left behind by the owners was a nice touch as well. It is very well located, and we walked everywhere we wanted to go in Porto. Many of our trips started at the Confitiere de Balhoa located just a couple of streets away, which sells a lovely selection of pastries!
The only possible downside is that the walls and floors were quite thin, so we could hear footsteps and general noise from the apartment above. However, I suspect this is the case for most of the (mainly old) buildings in Porto and it did not impact the enjoyment of our stay.
Would definitely recommend to friends or family looking to visit Porto.