We spent a very nice week at Dan's place :-)
It is very well located at just 2minutes walk from the center, and the city is fantastic !
Communication with Dan was excellent: we had independant problems with our flights but he was very flexible and quickly help us to find convenient solutions.
For a family like ours it's perfect: no stairs, an entrance for trolley, no noise, a very (very!) big bed and lot of place for putting clothes.
The swimming pool at just 50meters is the best I have ever seen for children !
If I come back in Vienna, I really hope it will be possible to come back :-)
Aurélien