We (wife and myself) visited our son and daughter-in-law for several days in Oslo and selected Christoffer's apartment because it was nearby. It is also perfectly located for getting around the rest of the city. Carl Berner Plass is a hub for transportation and the Oslo subway has an entrance just feet away from the apartment. It's very easy to get there from the Airport Express train. Plenty of neighborhood food shopping although you probably want to hop on the tram or subway for more elaborate restaurant meals. The apartment was as described in the posting. Laundry was in the building basement (and free) and there was a simple reservation process that made getting it done easy. We were shown how to navigate the process when we arrived.
The apartment was clean, well equipped and Christoffer's communicated well from renting to arrival and departure. We would definitely stay there again.