I strongly recommend Gerrit's apartment. The location is amazing (guess 100m from Metro) with good communication to city center.
We were in 7 (4 adults and 3 children) and all of us stayed well accommodated. The apartment was very clean, kitchen well equipped, 2 nice bathroom, good internet and garage place (which is not so easy to find out).
All important information was sent before our arrival, just everything perfect.
Appreciate Gerrit and Julie's attention and hope others enjoy and had a good time in Vienna as we had.