A great apartment in an excellent location. The apartment is on the second floor of an older building which has been newly refurbished to high standard, and has everything you could need for a short stay, including powerful aircon which was much appreciated. The apartment is high-ceilinged, clean and bright and all the fittings are high quality. The bed is extremely comfortable!
The apartment building is located on a pedestrianised street with a choice of cafes within a minutes walk, and supermarkets two minutes away. There is also a left-luggage store (in Patio d'as Maria delicatessen, 269 R. de Cedofeita) just up the road if you need it, very useful for your last day - you can then take a ten minute walk to Lapa metro station to get back to the airport.
All the major sights of Porto are within walking distance - you can be at the river side in 15 to 20 minutes, or the Crystal Palace park in 10 minutes. The only place we needed to take a taxi to was the Serralves art gallery and park.
Communication with Mimi and Claudia was very straightforward. All in all, highly recommended.