We loved Kilian's apartment.
It is spacious, bright, very comfortable and super clean. Everything worked fine.
Our only disappointment was that the fireplace was off limits. We were very much looking forward to cozy evenings by the fire.
It is not in the very center of Vienna, but а metro stop is very close and so are two tram stops. We ended up liking the location and it was fairly easy to get in and out of the city.
The apartment itself is very quiet and we weren't bothered by neighbors much.
Communicating by email was not very efficient, but text messaging worked fine. For us it was a bit inconvenient since we didn't have a phone in Vienna, but only internet.
Otherwise everything was great and the cost is reasonable.
We would love to stay there again.