The flat and the view is actually much nicer than what his profile pictures say. We stayed in his flat for seven days and really really enjoyed it. You are right in the middle of everything. We never used the underground. Everything is in walking distance. The flat is quite big with high ceilings, great modern furniture and a lovely bathroom. The view might be one of the best in town. Overlooking a small, but stunning olive tree park from the birds perspective. This park has shops underneath and I'd say it is an architectural highlight in Porto. We definitely can recommend to stay in Felipes flat.
Tipp: Rent bicycles at a shop called Vieguini in down-town (Reservation recommended). Super lovely and helpful people. Go along the south coast to 'Capela do Senhor da Pedra' and back.