Four stars is fair for this apartment, I think.
The PROS:
Location is excellent. 5 min walk to Karlskirche, Musikverein, Belvedere; 10 min walk to Staatsoper.
Apartment is very clean.
Wifi is fast enough.
The CONS:
The list of amenities includes a microwave and an iron; these are not present. When asked about this, the host did not answer. Which is whatever, just unfortunate (I didn't iron any shirts before my trip, anticipating there being an iron present).
The elevator is silly (fob to call the elevator and to press a button inside) and rather slow.
The building looks run down on the inside but again this is me being nitpicky.
One of the rooms smelled of cigarette smoke; this is not necessarily the host's fault but still unfortunate for my friend who had to stay in it.