We stayed for a week in Thomas' place, a renovated appartment in an older building located 10 min away from the center (via tram).
It is a modern looking flat that had more than enough space for the 2 of us, with a spacious living/dining room, an equipped kitchen, one bedroom and a small WC.
It has all the commodities you may need, including a dishwasher and a washing machine and quality Wi-Fi. The only mainstream electronic device it is missing is a TV which is something that we don't care, but some of you might.
If the flat seems nice to you, Thomas is nicer. Frequent and clear communication, he helped us navigate our way in Vienna .
To sum up:
THE BEST: Thomas as a host.
THE GOOD: Good value flat, with all the commodities we need.
THE OK: Location, but only if you really need/want to be in the center. We never had any issues as the tram runs frequently.