The location is great for walking around Porto and right next to the Trindade metro stop. The apartment is just up a less trafficked side street, but was still busy enough where you always felt safe. There are a few inexpensive restaurants within a few minutes walk that the locals frequent.
Maria was very responsive and pleasant to work with. Check-in was fairly easy. You have to pick up the key about a 10 minute walk away down a busy street, which was off putting as we were dragging our luggage behind us. Alternatively, you can have the key delivered to you, but there is a 10 Euro charge for that. The apartment was spacious and clean. It's clear it had recently been renovated making it feel very modern. The bed was comfortable. We didn't do any cooking, but the kitchen seemed fairly well stocked if you're planning a longer stay. All in all, we had a great stay without issues. I would likely stay again and I would recommend Maria and this listing to others.