Nice apartment with everything you would need for a comfortable stay in Vienna. We were a group of 5 (3 female and 2 male) and the space was just right for us.
The centre is easily accessible by tram and there's plenty of shops and places to eat nearby. There is a SPAR supermarket nearby so you can stock up on any essentials. Note - all the shops in Vienna close by 6pm on a Saturday and don't open at all on a Sunday - we hadn't researched this beforehand so it was a bit of a shock!
The living room was particularly nice with large windows, comfortable sofas and a large TV. Ferdinand was quick at answering our questions prior to arrival and the guest handbook was very useful.
The only improvement I would make is perhaps installing a curtain or something at the entrance to the bedroom on the middle floor as there is no door so you can see right into it as you walk up the stairs to get to the kitchen / living room area.
Overall we really enjoyed our stay and would highly recommend this apartment.