I found this place for my mother who visited Vienna from 3 days (we had a weekend together and she stayed for 3 days more - so I had a chance to see the place)
The apartment was recently renovated, I found out that Gerhard is the interior designer, who has done an outstanding work (to my opinion of course)
The place was very stylish, clean-cut lines, simple, meticulous and prestigious. Underfloor heating was very nice and comfortable
Location is excellent, 1 minute from Tram 49, 10 minutes from the subway - museum quarter, which also means the museums are within walking distance. BILLA - 3 Min SPAR - 1min, choose your favorite 
NEUBAU, which is my favorite area in Vienna is where the apartment is located - restaurants, cafes, shopping…, night life.
Gerhard was very responsive and late checkout was also available
Thank you Gerhard, will definitely recommend and come again
Shai