Very nice location with a spectacular view of Clérigos! Clean, well-maintained and (mostly) quiet apartment. Overall a great experience. Would readily book the same place next time I'm in Porto if it's available!
A few tips for the apartment and for Porto:
On the 4th floor (beware there is no lift, but those few steps are nothing compared to what you will walk if you want to see Porto).
If you have hired a car, as we had, note that you are unlikely to want to drive much within the city and parking is very expensive.