This apartment is awesome! It's super clean and has everything you need. What I liked most was the little WiFi dongle which you can carry around in the city. The location is very good, the museums and opera are just a little walk away. It is a safe neighborhood.
Check-in and checkout were uncomplicated. I came a bit early in the morning and I was able to leave my suitcase there until check-in time.
The communication with the owners was uncomplicated as well. Messages were replied to very fast.
I recommend this apartment for everyone staying in Vienna, however long your visit might be.