We stayed here for 6 nights, June 10 through June 15, 2013. The location, a block from the Opera and the Karlsplatz Ubahn station, couldn't be better.
The apartment we had (407) was spacious and comfortably appointed, with a bedroom completely separate from the rest of the apartment. Climate control was the best I've ever had abroad, with separate... what people say » (and effective!) controls for the bedroom and living area. The kitchen had all the necessary equipment and a very nice breakfast nook. (There's also -
The hotel was extremely conveniently located with the Opera House in the next street across, as was the Metro and trams and the main mall and there is a supermarket across another street. (We took the Metro to the CAT (City Airport Transport) station very easily with suitcases where we checked them in before boarding for the airport.) The staff were very nice and always helpful. The rooms were very clean and had great soundproofing.