The appartment is as described in the listing: a small appartment on two levels, with a large roof-terrasse. The appartment is nicely furnished, clean, and perfect for someone alone, or for a couple. I did not have the chance to meet Alexander but I met his nice mother, living next door, who let me in and showed me around.
The neighborhood is quite and residential, with nonetheless several restaurants in the street, and is next to the very nice Naschmarkt. For what I was interested in, it is also 10 minutes walk away from Technische Universität Wien, making it a great accomodation for an academic visitor.
Overall, the place is definitely worth renting!