TL;DR - If available, book this place. We could not recommend it enough.
The apartment - Might just be the best we've stayed in. The pictures don't do it justice. 7th floor with an elevator, designed in great taste, has all the amenities you could hope for in an AirBnB, plus your very own rooftop with the best view of Vienna, including St. Stephen's cathedral (tip: don't go up the 343 stairs, view's not worth it ;) ).
Location - Very central. Right on the Ringstrasse surrounding district 1, a few minutes' walk from some of its main attractions, such as Hofburg palace, Parliament and Michaelerplatz. Easy access to other parts of the city via public transport or - in most cases - a leaisurely walk.
The host - Jacqueline is everything you can hope for in an AirBnB host. Unfortunately we did not have time to meet, but she was extremely communicative via text messages and really did her best to make us feel at home. Lots of tips and extra treats we will let you discover yourselves ;)