The apartment itself was beautiful - a lovely old building, with high ceilings and a pretty courtyard. The location is also perfect - close enough to the Innerstadt to be within walking distance of everywhere you want to be (Rathaus, Hofburg, Belvedere, Stephansplatz), but just a bit removed so it's not too busy / touristy (on hot Summer evenings it's nice to hang out in the square outside the Karlskirche).
The room itself was good - there was a desk, some shelf space and a fan.
I have two criticisms - the wifi in this room is quite weak, which was a problem as I had to do some work for a few days. the connection is much better in the verandah area. The kitchen did not smell great either, I think because nobody had taken the bins out for a while.