Great, central location and easy communication with Carlota.
The apartment is quiet, very cozy and located in an authentic building. You've got all the amenities you need and a nice view to wake up to. There's a small supermarket in the street and plenty of places to eat and drink. There's also a metro station nearby so it's very easy to reach from the airport. (about 35 minutes I think)
Like other people have mentioned there's no elevator and there's quite a few stairs. For me that wasn't a problem at all, but it's something to consider if you're not as mobile or expect to leave and enter the apartment a lot. (I tended to leave in the morning and return in the evening.)
There were a few areas that could have used a little more cleaning (drawers in the kitchen, inside of washing machine, …) but overall everything felt clean. I arrived a few hours early then planned, so that might have been it.
Overall I would recommend this place and if I return to Porto I'll consider staying here again.