Spent three days here, the location is easy to find and very centrally located within Porto - a very short (<5 minutes) walk from Trindade Metro station which is convenient if you're arriving by train or plane. Trindade is also the main hub on Porto's Metro network so you can get all over the city (including to the beach) from there.
Check in was easy - the instructions sent by Aposentus were very easy to follow.
The flat is incredible - very clean, and absolutely enormous (I'm from London so anything bigger than a wheelbarrow is enormous to me). The bedroom is separate from the kitchen area, with plenty of wardrobe space and a large window fronting out onto the street (the street is not busy or loud at night, and in any case the windows are noise-cancelling).
The kitchen has everything you might need: a hob, oven, microwave, large fridge/freezer, and plenty of cupboard space. There is an open-plan lounge with a sofa and TV which can access Netflix.
I would recommend this flat to anyone staying in Porto.