The location of the apartment is excelent, close to Prater and close to trams, trains, subway, walking distance from the river and from the city centre. The apartment itself is very large (bigger than on pictures), with plenty of storage, excellent for a couple. We only spent 3 nights there while visiting Vienna and we didn't need to use the kitchen so we can't say anything about this part of the apartment, but the rest of it was really ok. The furniture is not chic or especially pretty but the standard is ok for a rental apartment and temporary stay.
We didn't meet Robert (his employee met us at the apartment), but there was a very good contact with the hosts via AirBnB and phone. We arrived very late at night (at 1 am, which was even later than planned), but there was no problem with late check-in at all (although it was paid extra 25€ which was agreed before arrival). Overall very positive experience.