First of all, the location of the Thon Opera Hotel is a very good one. It is directly across from the central railroad station, which is very convenient when you come in on the train from the airport. Short walk, no stairs, great. Then, though you might expect noise from the station, there is none, one of the nights we stayed there our room overlooked the railroad and we had no problem. On the other side the view of the beautiful Opera House and the water is quite spectacular. Proximity of the Opera House is a great plus for performances.
The rooms were not too big, not too small, beds super comfortable and a great bathroom. Enough closet space and enough hangers (not always easy to find!) The restaurant was good, interesting foor, but the breakfast buffet was just wonderful! All sorts of delicious foods, including herring in different sauces, smoked salmon, an omelet station and a wonderful variety of breads and cereals. Well worth the price.

I stayed here for one night in November 2011. The hotel staff couldn't have been more helpful. The rooms were great and very comfortable. Breakfast was a wide selection of hot and cold buffet.

We were looking at the conference facilities for a work event in 2012 and the conference facilities were great and the staff couldn't have been more helpful.

Location is a bonus, right next to the main train station with a Airport Express train that goes to airport in approx 20 minutes, very easy. I would definitely stay again.

Fantastic location for the City and the train and also great views over the Opera house and the harbour. Great Wi-Fi access and the breakfast was fantastic. Just a little expensive

We had the smalles room I think, but it vas good and clean. Also very nice. No problems at all. The service was okey. We did not speek to the staff so much. The breakfast was also great. A lot of different food and it was never empty!
Good choice if you are looking for a hotel in Oslo which is closeby almost anyting in the heart of the city=)