We (two sisters) stayed in Reinhard and Sabine's apartment for 4 nights.
We really, really enjoyed our stay there!
A new apartment in a bright, accessible building on a main street but the apartment is internal and very quiet. The apartment is very well maintained, clean, and has everything! The two double beds are very comfortable, and the apartment owners' communication is fast and excellent!
In addition, the location is also excellent! Three minutes walk to the metro station (now it's under renovation) and about 7 minutes to two more stations. Five minutes from Nashmarket, at the end of the street is the famous street Mariahilfer from the side of the Museum Quarter.
In short highly recommended!