We had a fantastic stay in Seville. The apartment is just as described and is a great base for a city break. The location is definitely the main selling point as it's right in the old town, a short walk to all of the main sites and bars/ restaurants.
The roof terrace is nice, although very hot in the day time with little shade.
The air conditioning in the apartment is great and very quiet- something of a novelty for those from the UK!
One downside of the apartment is that the wifi is very weak and we struggled to connect. We expected this from reading other reviews, but this is something to bear in mind if you will be needing to rely on wifi.
The apartment is on a quieter street, but we still found it quite noisy until 1am or 2pm with people walking to/ from their nights out. This would surely be the same if you're staying anywhere in the area, but we'd recommend ear plugs if you're a light sleeper.
Across the street there is a Día mini supermarket, which is handy for essentials, but there is a cheaper and better stocked Mercadona within a 20 minute walk.
We stayed for a week, which gave us time to also go on day trips to Córdoba and Cádiz. The train station is easy to get to and is only a 20 minute walk.
A long weekend would be plenty of time to explore the city, but equally there would be lots to do for a more extended stay.
We'd highly recommend this airbnb for couples wanting to stay right in the heart of the old town in Seville.