We loved the apartment. It's exactly as it is in the pictures and everything works perfectly. We especially appreciated the location, close to Wien Mitte, since two trains take you from and to the airport from there.
The apartment is very well decorated and it has many appliances to cook and even to wash and dry clothes, which is handy to travel lightly. Besides, you won't have problems with Wifi, temperature and water pressure at all.
It has a big double bed and a coach that become a double bed, so for a family of 4 is perfect.
We only had to take the metro to go to Schönbrunn, everything else within the main area of Vienna is within a 20 to 30 minute walk. So we walked.
The hosts were very attentive and quickly respond to anything.
Loved the apartment and would definitely come back since Vienna seems to be quite a neverending experience.