The apartment is perfect. We spent there 3 days and we felt like if we were at home. The location is absolutely wonderful, just 2minutes walking to Heldenplatz, Oper, Maria Theresien platz, Museumsquartier or even U-bahn2. Other tourist sites are also very close: Rathaus, Stephansdom, Karlsplatz...
The checkin and checkout were also fine, without problems. Anna & Vladan were in touch everytime we had some doubts and they left some recommendations of restaurants near the house.
Definitely, i would come back.