My stay in David and Silke's house was very good. The house is brand new, with everything you need to live comfortably and even basic necessities and cleaning products. There are a lot of details.
The house is very close to Hietzing station - underground line U4 - and from there to the centre - Karlplatz - it takes about 20 minutes. The Schonbrunn Palace and the Tiegarten are within walking distance.
The communication with them has been quick at all times. I highly recommend this accommodation.