My mom stayed at one of the rooms with a balcony on the first floor and really enjoyed staying at Hotel Capricorno. The staff is super friendly and helpful with any arrangements we had to make (taxi, train ticket, maps). The room was decorated in a very modern, but not too noisy pattern, and the bed was really comfortable to stay in. I loved the large window that overlooked the Donau canal and trams. Bathroom has good selection of amenities and the shower pressure was fantastic. Since the hotel is located next to Subway sandwich, the room smelled like freshly baked Subway bread - if you are not into that, you might want to ask for a room that faces the other side.
When staying at this hotel, make sure to eat the breakfast! The breakfast buffet was very well stocked and we really enjoyed the varieties of hams, cheese, granola, bread, juice, etc.
But what trumped all was the location of the hotel. It is located near all major transportation stops (subway and trams) and also was within a walking distance of main tourist attractions. Shoenbrunn Palace was also just a 20-minute subway ride away.
Overall, this is a fantastic hotel, and I definitely recommend to anyone going to Vienna.