In case you're still wondering whether you should book Andreas' place - there's nothing to wonder - just book it already.
The apartment couldn't have been a better place for us to spend a magical Christmas weekend in Vienna. First, the location is the best one can wish for - 2 steps away from Stephansplatz with an Ubahn station and lots and lots of shops, restaurants and bars all around - you really can't get more central in Vienna other than this.
The apartment itself is fantastic just as well - equipped with lots of great amenities, whether you're interested in cooking or in entertainment, and feels extremely authentic, aristocratic and high-end. We almost didn't want to go outside and explore the city because it was so comfortable staying inside. Although it wasn't much use to us in December I also figure having an A/C in both the living room and the bedroom is a blessing during the summer. Also the building itself was absolutely beautiful and it felt amazing and humbling to stay in a building that was built in 1720 (yet still had a modern feel to it inside).
Finally Andreas himself was the best we could have hoped for - he made sure to answer all our questions quickly, give us all the recommendations we asked for, specific instructions, wait for us at the Ubahn station and generally was very helpful and fun to talk to. He even made our stay all the more special by remembering we were also celebrating a birthday on that weekend.
If you're coming to Vienna - this is your place to stay at.