Diego was very flexible about check-in times, which is great when you're unsure about your arrival time. Upon arrival, there was a bottle of water and some fruit up on the counter which, I don't know if it's standard procedure but it was a very nice (and useful) gesture :)
There's not much I can add about the listing itself. Everything's clean and as described, quiet location but still in the city centre. If you need to work, like I did, the internet connection will not let you down. The space is just nice and cozy and you'll probably want to bring the bed home with you. The only thing I wasn't aware was that the whole building belongs to Diego and everything is rented. So, you might hear people coming in and out, which is absolutely fine.
At check-out, Diego was kind to keep my stuff in the building so I could go around the city free-handed until leaving Porto.
I highly recommend Diego's place and whish him all the best of luck for the future :)