We stayed there two weeks. Lovely apartment, very clean comfortable and well equipped. The host has the sense of small details that please. We liked the Mozart CD (of course) put on the table with other information and tips given to guests.
The apartment is well located. One of the best place to stay in Vienna, typical and very "trendy". A nightlife well supported by cafes, bars, various restaurants with terraces etc. We have a principle: "eat where locals eat". Feel free to stroll along the narrow streets just west of the Museum Quartier between Burggasse and Siebensterngasse.
In addition, the host has very good recommendations regarding good food nearby.
Apartment is near the city center, shops and all transport (tram, bus, metro). But we walked most of the time, so it's nice to wander day and night in the small streets of the city center and the neighborhood.
The host is very attentive and meets all your needs, advice on transport, interesting places to visit etc.