My friend and I had a great stay. The apartment was clean, spacious and modern. The king size bed in the main bedroom was comfortable, and both bedrooms had plenty of storage space. The single beds in the second bedroom were long enough for adults to sleep in. The apartment was well-heated, but the heating level in each bedroom was adjustable. I didn't use the kitchen much, but it seemed well-equipped.
The location is very good. It's a short walk to the U3, which goes to both the old city and to Wien-Mitte station for trains to the airport. It's also within walking distance of the main museums and the old city. The main shopping street is nearby. There is a French cafe-restaurant next door that has a nice brunch buffet on Saturdays and Sundays. There is a traditional Viennese cafe not far away.
Thomas was very friendly and gave us good recommendations.