We (colleague and I) stayed at this place for a week for a conference at the Vienna Convention Center. It is a 10-15 min walk from the Hauptbahnhof, or there are one of two trams which stop right across the street and around the corner to get to/from Hbf and U1. Heydrich met me to let me in and show me around. Apartment was great, definitely big enough for the two of us and could probably have comfortably accommodated more travelers as well (if you like each other). Kitchen was great, the induction cooktop heats very quickly. Only thing was I noticed my laptop would sometimes drop the wifi in the second bedroom, but I had no issues in the common area. There was even a small patio, but it was a bit cold and a busy week so we didn't use it :) The hallway could get a bit smoky (because Vienna), but it didn't get into the apartment. Gracias a tod@s!