We`ve stayed at Observatoriegata 13 - it is great location, just one cross street from Aker Brygge, and few minutes from Karl Johans Gata.
As in most similar places rooms was looking like from Ikea cataloge - so you need to be prepared for this. Apartament was very spacious, quiet and well equiped. There is heated floor in bathroom, washing mashine and dishwasher. Very fast, free wireless wi-fi is huge plus.
If you like to have high temperature in your room is not a problem - just turn your radiator to higher temperature (even to 30 Celcius degrees). If you would like to watch TV - you can use big tv that is located in sitting room.More