We stayed for four nights at the Hotel Capri in July and we enjoyed our stay very much. The room was large and well equipped (comfortable bed, flat screen tv with channels in many languages) and the bathroom looked brand new and very clean. The people at the reception were lovely and friendly, offering information each time we needed. The breakfast was rich and offered a wide selection (from fruit to cereals, yoghurt, many types of cheese, bread, jam, honey... anything you could wish for, plus coffee/espresso/latte macchiato).
The neighborhood is quiet, civilized, there are supermarkets down the street, and it is a short walk away from the centre (Stephansdom) and from the Prater. It also has a subway station right in front of the hotel, leading to the centre.
Overall it would say the Hotel Capri was the best choice and that we had an excellent stay. I would definitely stay there again on my next visit to Vienna.