Our stay at Alexis' was good, the apartment is small but just fine for a city trip. We'd rather recommend it for a family with kids, for four adults one of the double beds might be a bit small.
The apartment is located in an amazing neighborhood, there are a lot of great restaurants, cafés and tapas bars around the corner, as well as a lively market. However, the apartment and the building were exceptionally quiet. The city center, the shopping district and the most famous sights of Sevilla are about 15 to 30 minutes away by foot.
Be aware that the bathroom is a little smaller than it looks in the photo, but has a very spacious walk-in shower and everything you need.