My partner and I spent a week in Gerard & Nicole's flat in Vienna and it suited our needs perfectly: a great location close to the centre with a local neighbourhood feel, a beautiful flat that was a great size for the two of us with everything we needed and hosts who were always available if we had questions or needed anything.
A friendly and engaging Gerhard met us upon our arrival to help us get properly settled and give us some very helpful advice on places to eat at in the neighbourhood, etc. Communications from the start were good and they continued to check in on us to make sure everything was going well during our stay. I would definitely stay with Gerhard and Nicole again if ever back in Vienna and highly recommend their place.