Lukas place in Vienna was exactly what we needed. It was very spacious (our family of 5--2 adults and 3 children under 10) fit extremely comfortably with plenty of room to spare. The location was good because, although it isn't right in the city center, there are things to see close by, nearby train stations with short rides to key sites/areas, grocery stores nearby, etc. It was also very nice having the washer and dryer since this was the last leg of a long central Europe trip and we had plenty of laundry to do. Both worked perfectly. The beds were comfortable, the Wifi worked great, the home stayed reasonably cool even though it was quite warm while we were in Vienna.
The two best things about Lukas' flat in Vienna are how spacious it is (2 bedrooms with several beds, a family room with more beds, a large entry way, and a full kitchen) and how accommodating Lukas is as a host. He was extremely easy to communicate with, answered questions quickly and completely, gave us a great walk through of the apartment, and was extremely flexible with our check-in and check-out times.
I would recommend Lukas' apartment if you are a large group coming to explore Vienna.