The flat is perfectly located right in the centre of Vienna, with a view on the Danube. There is a metro stop just outside the flat but you can basically walk everywhere. It is very easy to get to and from the airport.
The flat was spotless. It was really nicely decorated and had everything we needed. We particularly liked the kitchen design. Although it is in the centre, it was really quiet and we slept very well.
The host provided us with detailed instructions for check-in/check-out and directions from the airport, and replied very quickly.
We would certainly stay there again and highly recommend it.