Unfortunately we were not able to meet Chris upon our stay in Vienna, but his father met us to give us the keys to the apartment and he was extremely friendly.
Positives about the apartment include: good connection to transport links (U-Bahn U4), apartment inside looks newly redone - nice bathroom and kitchen area, apartment was well stocked with clean towels, coffee, tea, sugar, kitchen utensils and plates, etc.; it was nice to have the entire place to ourselves, there was a fan which was nice to cool down the apartment since it was so hot outside
Negatives: there was a slight smoke smell throughout the apartment although there is a no smoking sign, I assume this was no fault of Chris's and was most likely an uncompliant Air Bnb customer; the apartment is in a run-down building (although inside the apartment was nice), it is a VERY small studio apartment which isn't necessarily obvious in the pictures, there was some noise outside the windows if they were open (it was hot so we had to open the windows)
Overall, Chris's place was safe and comfortable, and was a great price for a two night stay in Vienna.