Anna (ably assisted by her cousin Marianne) was a fantastic host. She was always prompt in her responses, and very easy to deal with. Marianne went out of her way to make our check-in as easy as possible despite my early arrival, and kindly stored my bags and the bags of another friend who was not able to check in to her accommodation until later the same day.
The apartment is exactly as it appears in pictures - large, airy and full of old-world Viennese charm with Anna's personal style throughout. It was the perfect apartment for us - as a large group of 8 split across various accommodations on Vienna, it was perfect to have such a large lounge space to meet for the nights we were too tired to go out. We were comfortable with just 3 sleeping at Anna's apartment, and bedding would easily allow for 4 (so long as you are happy to share a bed). The lounge is large and very comfy to sit on, but I imagine it would not be great to sleep on for an extended length of time.
The facilities were all great and as pictured/described. The location is absolutely perfect, right in the heart of the old First District and with easy access to public transport at Stephansplatz, Schwedenplatz and Wien-Mitte.
In short, the perfect apartment for your stay in Vienna!