Eva & Friends apartment at Operngasse street is a nice apartment in a great location of Vienna's Wieden district/neighborhood (The Guardian's article about Wieden: https://www.theguardian.com/travel/2015/may/21/emma-john-wieden-vienna-austria). Apartment is close to the number of traditional tourist attractions - basically at walking distance: Kunsthistorisches Museum (Rembrandt, Bruegel brothers, Caravaggio et al), Secession museum (secession architecture, Klimt's fresco's), Hofburg palace, Belvedere palace (secession, expressionist painters), Vienna's Operahouse etc.
Since I was visiting Vienna for a conference, which took place at Technical University of Vienna (TU Wien), it is worth noting that a flat is very close to a TU Wien campus - 10 - 20 min walk.
Furthermore, it has very good location with respect to public transport - 10-15 min walk to the underground/subway station (2 lines leading to main railway stations), tram/trolley, and bus stops.
I personally enjoyed the urban life atmosphere of the Wieden neighborhood. Particularly the building with our flat, the streets with secession, modern architecture, rich choice of the various cuisine, bars/pubs, coffeeshops, groceries, and famous Naschmarkt with bakery, restaurants, fresh produce.
Eva and friends are very friendly, helpful, and considerate hosts. They provided all the necessary and useful information - about apartment policies, public transport, dining etc., and promptly answered the messages. The apartment was clean, nice, with all the necessary appliances, so that guest can prepare his own food. Anastasia, who met us on a first day to hand a key and greet us, was punctual, very friendly, and generously gifted us a bottle of wine.
In a summary, we have enjoyed our stay in Eva and friends' apartment, and we sincerely recommend it.