My family and I had a terrific stay in Vienna, and we thoroughly enjoyed ourselves!
The apartment was located just steps from all the major sites around Vienna's Inner Stadt. We walked to our the museums and sights we intended to visit, and when we wanted to visit something a little more out-of-the-way—such as Schlöss Schonbrunn or the Zentralfriedhof—the U-Bahn stop at Stephansplatz connected us to any tram, train, or bus we needed.
We were able to pack light and use the washer in the apartment; we also shopped at the local Billa (market) for groceries so that we didn't need to eat out for every meal. It was cold outside (about 38–40º F), but it was nice and warm inside when we arrived home each day.
We were a bit later to arrive in Vienna than expected (due to a canceled flight), but our hosts responded warmly each time I wrote to update them of the changes. They also provided great recommendations for Wiener Schnitzel. I would not hesitate to recommend staying here to others!