Kaspar's apartment is even better than in the photos, and provide a great view of the Viennese sunset. It's not completely in the city centre, but right next to a metro station and a tram station, which provide great connectivity and make the location great anyway!
Overall, I think this is a great place to stay while experiencing Vienna. I would definitely stay again if I visit again.
There's also a late night bakery just below the apartment, which is good for night owls like ourselves.