Location, location, location. You will not find a better situated flat. We were able to walk to almost every attraction. The only exception was Schonbrunn Palace, which is a quick train ride outside of town.
The flat was very clean and even had a safe. Sarah's directions were clear, and she was responsive the one time we contacted her.
As pictured, the bed is in a small space and borders walls on three sides. It was extremely comfortable, even for my husband who has a bad back.
Overall, it was a great place to stay. I highly recommend it!