Excellent place—it's pretty much a penthouse, for the building. Top floor. Great views. Well furnished. Great amenities, including a Japanese bathroom. The pictures don't do it justice, sincerely.
And the location is perfect; from Praterstern, you can get wherever you need to in Vienna. You can walk to Stephansplatz, or it's a quick U-bahn there. You can also easily, like by just walking a block or two, get public transit to the Palace, Belvedere, main train station, or the airport.
If we come back to Vienna, we'd book here again in a heartbeat.