Stayed three months for business. Really comfortable place, very aesthetically decorated and well-supplied to meet all basic needs. The apartment is 5-6 min walk to U3 (the metro) which makes it easy to get to any point in the city center. The place was clean and quiet, with a view of a lovely courtyard.
Christina was a great host - thoughtful, helpful, friendly. She regularly checked to make sure my stay was comfortable, and offered many good tips for getting by in Vienna. I would highly recommend staying at her place.