Marco's place is fantastic. We could not be happier that we stayed there. Marco was a tremendous host and reached out to us on our train ride to Porto to make us aware that there was a football (soccer) match between our train stop and where his house located and that we should get off at an earlier stop. He even came and picked us up from the train station. This probably saved us a long wait in traffic after along plane and train ride.
The three floor condo itself is amazing and the view from the middle floor with a very large window into Porto is unreal, and as our daughter put it, like something from movie. It was completely worth the walk across the bridge into Porto (which is only a about 5 minutes) to have this view everyday (also the Port tasting tours are closer).
Just a note on the beds (a good one). To us from North America the beds in the Airbnb pictures looked like a wood base with a futon mattress on top, so potentially not too comfortable. When we first booked we thought that maybe this was a tradeoff against a really nice apartment with the best view you could have. Well, not accurate. For us, the mattresses were top notch and extremely comfortable.
Some other points:
There are four balconies that can be used
Their is a gondola ride right beside the apartment, it is very quiet and the apartment glass is one way, so they can't see you.
The bathrooms are very nice. There are a lot of different controls on the showers so maybe get Marco to show you which one does what. We ended up never using the shower in the second bathroom (we did not call to ask as the one shower was enough).
Would recommend Marco and this location to anyone.