This is a nice apartment in a really great location! A couple of minutes walk from Karlsplatz and the Naschmarkt. It was very clean and we got great recommendations for restaurants from our hosts :).
We did have one significant issue - the curtains are not sufficient to block the sun in the morning, so from 6:00am-ish the room was really bright. We mentioned this to our hosts, but there wasn't a solution available at the time. I hope they are able to solve this, because it affected our sleep.
Two smaller things -
1. The elevator only reaches one floor below the apartment, so there is another flight of stairs to climb.
2. While there was always hot water in the shower, we weren't able to make it stay at a constant pressure or temperature - it kept oscillating to hotter and colder, and occasionally dropped in pressure.