Absolutely loved this apartment. My friend and I only had a couple days in Vienna, but because this place is so centrally located we were able to tackle everything on our sightseeing list.
The apartment is literally a few minutes walk from the U4 metro line, which takes you to Schönbrunn Palace (a must see) and also the Inner Stadt, the city center with a ton of sights. You can also walk to the Inner Stadt (takes 15 min to get to the edge). It's also a few minutes walk to the historic Cafe Sperl.
Michael was very helpful during our stay and also made the check in process extremely painless.