The apartment is very quiet, in the second row of buildings, not directly in the street. It has all needed amenities, including haidryer, iron and ironing board, coffee machine, TV/Cable. The double bed in the bedroom was very comfortable, our friend sleeping on the sofa did not complain either. Everything was very clean, and much of the furniture is brand new.
Ross and Sonja were very responsive, provided detailed instructions before we arrived, and in the apartment we found some more useful info. The 'self-service' checkin and checkout went very smoothly.
Location is very good - a few minutes walk from the subway station, with a bus stop just in front of the building and trams nearby. However, many of Vienna's attractions are perfectly reachable within a 20-minute walk (opera, Museum District, Stephansdom). The area itself has a wide range of restaurants and cafes - from traditional Austrian to sushi and pho, some grocery stores are also close by.
The only downside is accessibility for the disabled/elderly (first floor only accessible by stairs) - otherwise, I'd definitely recommend this place for groups of 2 or 3 active travelers.