We stayed a for 4 nights and even with our awkward arrival date (1st Jan) everything went smoothly. Robert gave us some excellent information about the local area and how to get to the various attractions in Vienna. Getting around was very easy, there is a Tram stop right outside the apartment and the underground is around a 5 minute walk.
I would have no hesitation in recommending this apartment to friends and family or coming back to stay here again myself.