The Good:
The location is great, near the Cathedral and most places you would want to visit in Sevilla.
The host keeps the apartment spotless. Very clean and also very well stocked. Any issues that come up, I received a reply almost immediately. I also received really good instructions on how to get there and to other places. Very friendly and accommodating.
The Bad:
The apartment does not have much natural light. It might be good to keep the summer heat out. What really was horrible was the noice from other apartments, also airbnbs. The windows that open open towards the inside of a small patio, closed all around. Guests would open their windows and smoke, have loud conversations, until 3 am 3 of the 4 nights I stayed there. The host contacted them after the first night when I complained, but it did nothing. If staying out all night is part of your plans, then I recommend this place. I had to work, though, and it ruined my days.