I stayed at the hotel Carlton for 3 nights, and thought that it was good value for what i paid.
The room was small but clean, the only thing that wasn't good with the room itself was the bed,i had booked a double bed, and found that it was more or less two single camping beds that was pushed together.
Apart from that the staff was very nice and helpful, and the breakfast was ok.
I would recommend this hotel, as it was good value for money, and it is located in the center of Oslo.