I had the pleasure of staying in Karin's apartment while visiting Vienna for the first time with an old friend. We both thoroughly enjoyed how lovely the space was, and how conveniently located it was.
The apartment was exactly as lovely, calming and peaceful as the pictures show. Karin met with us personally to let us in and show us around, and she left us with a welcoming bottle of wine! The information she gave us was exactly what we needed to get out and start sight-seeing immediately. The apartment itself was very well-located; we took either the subway (7 minutes walk from the apartment) or the tram (2 minutes walk from the apartment) to make the short trips to all the sights we were interested in seeing. The apartment is on a busy street, and the trams run right outside, so if you are extremely sensitive to noise then this might not be the right choice for you. I found that simply closing the window was sufficient for blocking any street noise.
Karin was a marvelous hostess. She responded to texts very quickly, and had lots of good information for us. On our first morning, she stopped by quickly to drop of some freshly-baked local bread- that was quite a treat!
One other thing I should mention is that this apartment is up two flights of stairs. My friend is an elderly lady in her 70's, so I worried that I had made a bit of a mistake. But she handled the stairs with aplomb, and Karin's husband, who came when we were checking out, was kind enough to carry her suitcase down for her.
In all, I would thoroughly recommend Karin's apartment for its comfort and beauty, its very helpful hosts, and for its convenience!