My boyfriend and I stayed at the apartment for 5 nights and overall it was a positive experience. The apartment was very clean, spacious, and modern. We got to check in early which was great since we arrived in Porto around 11AM in the morning and check in is normally after 2PM.
It's relatively close to the center, approximately 15-20 minutes walking to a more central touristy area and about 35 minutes walking to the river or quick metro trip away (15 minutes). It's definitely in a more "local" neighborhood, and is located on a somewhat steep cobblestone street, which might not be for everyone, although was fine for us.
I have to agree with some of the other guests' reviews that the bathroom with the shower did have a musky/strange smell, and that water gets all over the bathroom since the shower is level with the rest of the small bathroom. It was convenient to have the smaller 1/2 bathroom for these reasons. It was also a bit cold in the apartment, since there is only one electric heater for the entire space. I also requested a hair dryer since there wasn't one in the apartment as advertised, but I didn't get a response. Surely if these few things could be fixed it would be an even better place to stay!