Our group consisted of two adults and two fussy boys aged 8 and 5. The apartment was bright, very spacious and in a great location, less than a minute from a very frequent tram line into the city centre and close to lots of shops and restaurants although almost none of the shops are open on Sunday so be prepared for that (there is a small but well stocked Spar open in Karlsplatz U-Bahn station on Sundays about 10 minutes away by tram).
The floors below the apartment seemed to be all offices which I wasn't to sure about initially but was very much a positive as it afforded a degree of privacy and everyone we met was very friendly. Our boys loved the "upside down" nature of the apartment with the bedrooms and bathroom downstairs and the eating and living area upstairs to take advantage of the huge ceiling windows and balcony, we got to sit on the sofa and watch a lightning storm through the window on our first night there.
The beds and sofas were very comfortable and everything was very clean. The instructions we received in terms of location, amenities in the surrounding area and how to check in were incredibly detailed, clear and easy to use.