Excellent place to stay, modern and very comfortable.
Wolfgang is a great host and very helpful - we had an early arrival and had no problem with leaving our luggage in the apartment before checkin. He also helped us out with a small issue with the air-conditioner and communication was quick.
Kitchenette is small but functional - only setback is that a couple more cups and glasses would have been nice.
Location is very good, close to Westbanhof station and a tram stop (MariaHilfer Gurtel) is just right down the street. Overall a great place to stay and would not hesitate to use it once more if visiting Vienna again.