Daria & Jochen flat is great, roomy and bright. It has enough space (i was staying for business with 3 colleagues and we all had enough room & intimacy) and it is well located. Daria was a very friendly and welcoming hostess, adapting to our needs (check in - check out) and responding questions in no time.
I would suggest the flat for family or 4-6 people groups staying in Vienna, and I will definitely come back if opportunity occurs.