I spent 4 nights with my family in Harry's apartment.
The apartment is located close to the public transportation (metro and train) and it is very well equipped. The house is big, quiet, warm and with plenty of hot water for the shower. However it is equipped only for 4 people, so I have to ask several times to Harry to provide us the fifth chair (as I booked the apartment for 5 people). So one person had to eat on the sofa at the beginning.
I have never met Harry, as I did self-check-in, taking the keys from another building near-by.
We found the house not prepared for 5 people as booked, so I had to ask Harry to bring additional blankets. Luckily it was morning, otherwise in late evening, one person would have not found the sleeping materials.
I must admit that the communication with the host was deficient: I have to ask several time the instructions for the check-in and my further requests for clarifications have never been met.
I also tried to call the host and the never answered, he replied only via sms and several hours later.
To sum up the apartment is very well suggested for the staying in Wien, while we are not did not enjoy the communication with the host.