We had a great stay at Anja's flat. Getting the key was very easy and we were able to leave our suitcases in the flat when we arrived earlier than planned!
The flat was very clean, comfortable and nicely decorated. We felt very comfortable at the flat and was well situated to explore Vienna. There's also several grocery stores nearby if you decide to stay in. We really enjoyed the location which had several shops and within walking distance to all major sights (we didn't use transit but walked everywhere so I can't speak to transit).
We loved Vienna and really enjoyed Anja's flat. We would recommend this flat to anyone staying in Vienna. The only note would be that it is a 3rd floor walk up for anyone with mobility issues.