The Cocoon Salzburg was a very nice hotel to stay at, especially with their environmentally-friendly approach. Staff was very friendly, and the breakfast was great (and semi-affordable at 18.90). The close proximity to the train station was great too, and the city was a 15-minute walk.
The reason for 4/5 stars is that although there was AC, it remained pretty warm in the room even when the temperature was supposed to be 18 degrees. Also, if you are a light sleeper in terms of light sensitivity - make sure to bring a sleeping mask!