This hotel has quite a lot going for it in terms of location (right by the National Theatre), ease to get to (tram 18 stops across the road) and nice enough communal areas, excellent breakfast with good food and plenty of choice, etc.
However, despite the staff on reception being polite and helpful on the surface, they really do make things hard for everyone.
We arrived early and, as always, asked if it was possible to check in or if we would have to wait. The receptionist then proceeded to check us all in to one room without explaining that only one was available. When we asked if we could check into all three rooms that we had booked we got the answer that we should be grateful to be allowed in to one - we were, this just hadn't been explained. At this stage we were told that the pool & spa were being refurbished but if we really wanted to we could go use the one at the other Radisson - not really the same we pointed out & our suggestion that we be provided with tram tickets to get there was met with a sneer.
When we got up to our one room (on the top floor that the lift doesn't even go up to - again this wasn't explained) we were extremely disapointed as it was really small. It was also a double room and we had booked twin rooms. However, we decided to make the best of it and went out for the day.
On arrival back at the hotel we asked to be checked in to our remaining rooms since it was now after 6pm and were met with "we'll see what is available" - what??? At this stage we were tired and had had enough. One of our group demanded to see the manager who suddenly found not only the remaning rooms twin rooms, but decided to upgrade us to business class - at last someone who understood customer service!!!
The business class rooms were good, but not excellent - I would have expected a similar standard in a regular room to begin with.
Overall, I would recommend this hotel witht he proviso that you don't expect the reception staff to look after you and demand to see the manager if you are not happy.

LOCATION AND COMMUNICATIONS
If arriving at Gardermoen airport consider taking the airport express bus instead of the train. It does take longer than the train but the upside is it stops right outside the main entrance and all you have to do is sit on the bus. If taking the train get off at Nathionaltheateret and walk up - it's about a 10 minute walk but can be a bit stressful if you have heavy luggage.

Tram 18 stops right next to the hotel and there is also a Hertz rental office at the hotel, which makes renting a car for a day or two easy.

For other public transport you need to walk for about 10 mins down to Nationaltheateret station, where you can catch buses, trams and the underground.

Note this hotel is not in a "happening" neighbourhood and there are not that many restaurants and bars in very close proximity - expect to walk for about 15 minutes or take a cab.

TIP:
Right across the street you will find a huge convenience stored called Deli de Luca. It's open 24x7 and has lots of good food and drink. So if you just want a snack, or don't want to order room service Deli de Luca is your saviour. They have sushi (usually pretty fresh), warm items such as lasagna, barbeque chicken legs, chinese dishes etc. which they just heat up in their industrial-size ovens. They also have lots of different kinds of non-alcoholic drinks, snacks and even essential household items such as dental floss, toothpaste, and headache tablets.

BREAKFAST
Good, but only average - and not as good as the Oslo Plaza. The breakfast room gets very crowded at times. Some of that is down to staff deliberately closing off some of the tables by placing 'reserved' notes on them. If only they could just open up the whole restaurant and use all the tables it would be a nicer experience for everyone. I bet they just don't want the extra work of having to clear more tables.

The food was not bad, but not very exciting either. Not much choice. Plus points for the omelette making station - but minus points for only having 3 items to choose from for your omelette.

ROOM
I am normally upgraded to a business room at Radisson hotels. This is the first hotel where I have had to phone down to reception and get them to confirm that I was in a business room! The room just seemed to small for being a business room.

Don't get me wrong, the room was quite nice. We were on a floor with recently renovated rooms and the corridor still had that 'new' smell you get. It seems Radisson made a conscious decision to put profit before customer satisfaction and made the rooms small when they refurbished them. They could have made them roomier if they wanted to.

The bathroom was good, so were the beds, and there was a big plasma with lots of TV channels. No sofa, just two uncomfortable small chairs and a small table. Desk was OK but could have been bigger for a bigger work surface - it felt a bit cramped.

SERVICE
The daytime receptionists were usually pretty friendly and helpful.

Room service seemed a bit chaotic and the food was just OK.

PARKING
The hotel has an underground car park operated by a company called Q-park and it's called "Slottsparken Parkeringshus". It does make life easier if you have a car - you drive right in and there is an entrance to the hotel directly from the car park.

Parking pro: Easy, convenient, great in winter - parking is heated so you always step into a warm car.
Cons: The cost. You do get a 25% discount but the price is still pretty steep.
Tip: Paying for the car park is cumbersome. When you enter the parking lot, take a ticket. You then need to have the ticket validated at reception before you use it to exit the car park, otherwise you will not have the hotel discount applied. Annoyingly you cannot get a ticket for your whole stay and get billed to your room, you have to get a new ticket every time you enter and then have this validated at reception. When exiting you need to insert your credit card. On the positive side - you only pay for the time you are parked there, not a flat fee per 24 hours as you might think. Another con: The lifts at parking lot level stop working from about 9.30PM to 7.30AM. Outside of those hours you may have to lug your suitcase up a set of stairs to reach the reception floor.

THE SPA
...is not really a spa. There is a pretty well-equipped gym with newish machines and a good aircon system. The swimming pool has seen better days and the water was a tad cold for my taste. The fresco painting on one of the walls depict a holiday resort somewhere in Africa and will probably offend anyone from that continent - take a close look and you notice the (black) locals gathered round a campfire next to their village straw huts while the (white) guests party away the night in a separate section. I hope they redecorate those walls and completely refurbish the whole pool area soon.

Staff at the reception very polite and helpful. Radisson Blu is centrally located, you can walk to all the primary and secondary tourist sites from it. Room was spacious and clean. Breakfast was included and excellent. There were no tea/coffee making facilities in room. The internet did not work.

Here's a hotel that's well located, has a direct bus service from the airport (Fylbussen) and has a lot going for it but blows it with terrible front desk staff and ugly rooms.

Apparently if you don't know, the staff will check you in to the 20th floor where the rooms are "terrible" (front desks' words, not mine) and you be directly underneath the rooftop bar. You will hear partying in the middle of the night and when you call the front desk to ask, they will tell you (at 1am) - "Please pack up, come down, exchange for a different room, and we can accommodate you".

"Accommodate me ? " You, Mr Raddison, are in the business of guest services. You should have run up with a staff member, key for a new room in hand, and helped me move. I did not pay $200 a night to get out of my pyjamas when I am jet lagged only because you gave me a "terrible room".

Pros (there are a few):
The room rates are about what you'd expect in Oslo (US $200) for average rooms.
The direct bus drop off that cost about US $20 (NOK 150) from the airport (bus leaves every 30 minutes)
Centrally located close to Palace park, within a mile of walking to Karl Johanns gate (main shopping and happening area in Oslo)

Cons(there are lots):
Apparently they have been undergoing renovation and if you don't know, they will check you into a terrible room. Mine was located on the 20th floor.

The room was small, hardly equipped with anything, cold (they needed to bring a radiator heater to warm it up), and had no coffee machine, the lamp fuses were blown.

The furniture looked like it was bought used in a college dorm sale. It was broken.

The staff is unapologetic about any mistake they made. First they will check you into a terrible room under the rooftop bar (in case you are not an avid reader of travel forums, how would you know?). Next day when they give you an electronic key that is not working on your new room, they will ask you to come down again to fix the key, rather than sending up one of the 6 people standing around on front desk talking.

What kind of customer service training do these people go through ? I know they are Norwegians and arrogant about their high salaries, high quality of life but at a hotel, your salary is being paid largely by the guests who come in and pay $200 or more per night.

The food options are few at the hotel. They have a hotel bar, and a small restaurant (Enzo). Very expensive, limited menu and basic stuff for $50 a dish so beware.

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My advice as a frequent traveler:

Do your research, find another hotel that may be a bit more expensive but give you better service and that with a smile.