Really enjoyed our stay at the flat, it was really beautiful and in a great spot.
However, the communication and check-in were a bit confusing. We were waited over 45 minutes at the door of the apartment. Luckily it was a nice day, so wasn't too much trouble. When I called GuestReady from the bus station, they didn't seem to know who we were, or which flat we were staying in.
When the person from GuestReady arrived, he didn't seem to know which of the flats in the building we were staying in and had to try a few of the doors.
With regards to noise, the upstairs neighbours' floorboards were a bit creaky, which did keep us up for a bit at night, as did the noise from people coming up and down the apartment block stairs. I can appreciate this is difficult to fix, but just something to be aware of.
Their free baggage storage was very handy and made our final day in Porto a lot easier.