They were really friendly. The location is perfect to visit Vienna. It was flawlessly clean in the whole apartment. The only reason we gave 4 instead of 5 stars (we would have given 4.5 if possible) was, that
We had to give up one of the two rooms for one night because her in-laws got there unannounced. But to be fair, we only really used one room because of the heat wave that time. They even bought a fan(ventilator) for us because of it. But there was "only" one so we slept in one room anyway.
We can strongly recommend that apartment.