Mariana was very responsive before our arrival, and was welcoming and helpful when we checked in (she gave us tips of things to visit). The apartment was clean, had a nice view, and was centrally located--although it was a little noisy with the sea gulls along the river, not respecting night hours! (we had to buy ear plugs to be able to sleep).
The one thing people may need to know is that despite there's a fully equipped kitchen with a great induction stove, there aren't any basic supplies for cooking or for breakfast (eg. oil, vinegar, or coffee/ tea) as is the case in similar apartments in other cities. This is surprising as this apartment is very likely to be booked for short visits.
Overall, I thought it was a little overpriced for Porto, especially because it is only a studio and because it doesn't offer these little advantages I mentioned (I've been in bigger apartments that had cooking basics for cheaper in Lisbon or Paris, France for example).