If you are planning a trip to Vienna I can only recommend this place.
While the apartment is not exactly in the city centre, the U3 subway station is just a couple of minutes away, and it takes around 10 minutes to get to downtown Vienna. There is also a shopping centre just two blocks away with multiple supermarkets and pretty much everything else you could need for daily life.
The apartment is not very large, but there is definitely enough room for four people. It's quite nicely decorated and the fully stocked kitchen came in very handy.
Margit and Herbert are amazing hosts and made us feel very welcome, leaving us some Viennese specialities and even a bottle of sparkling wine for New Years.
Should I return to Vienna in the future, I would love to stay there again.