This place has been extremely convenient for our stay in Porto. It is a large top floor with a large deck and views over the city on both sides. The unit is quiet, clean, and furnished with all necessary amenities. The wifi is fast and reliable.
The location is near the pedestrian shopping street of Santa Caterina, and it is central enough. It is not near the most touristy attractions by the Douro river, but it's only a 15 minute walk to go there. We walked to/from the place to go anywhere; it was easy to walk to the train station to rent a car to get out of town; or to walk a couple blocks to catch a bus to the ocean beaches for a day of surfing. The location is outside of the most touristy area that you can get good food for cheap. We were pointed to a nearby francesinha place that was touted as the best in the city (and that dish is a Porto specialty).
For the days when I rented a car, it was easy to park on the street (but parking is free only between 7pm and 9am).