This was one of the best places I've been so far (and I've traveled a lot). The place is cozy and has absolutely everything that you will ever need for your stay - kitchen equipped with everything important, nice clean bathroom, comfortable living room and a comfy bedroom. Location is amazing, since the subway is near, the Prater is 10 minutes on foot, as is the train station that gets you to the airport for far less money than the CAT train. The city center is again reachable on foot - 10 minutes. Neighborhood is very nice, we did not have any problems at all, or hear street noise. It was quiet. There are a lot of supermarkets close, but keep in mind that the closer ones close at 8pm.
We had an issue with the hot water and the heating when we checked in, but Pia (who is helping Markus with the apartment) was kind enough to react immediately and come to see what the problem was in person. It turned out that the heating will not be on for the night because of low pressure of the boiler that distributes the heating and Pia suggested to move us to another apartment in the same building, which, fortunately for us, was free for the night. It was a very good apartment too, bigger and on the last floor. And the heating was working! On the next day, the boiler was fixed first thing in the morning and we successfully returned to the apartment. I am really amazed at how well Pia handled the situation and with what she's done, I can tell that she is someone who cares about their guests and wants to make them feel comfortable. Not all hosts are like this and I really appreciate all that she did for us.
I definitely recommend this place to anyone who is visiting Vienna, it's an amazing place! Don't miss out.