We had five guests staying in Christoffer's place. He let me know it might be a little tight for five but that an extra mattress would be available (used for my 7 year old). It is indeed a compact space but comfortable and very well arranged. Also readily available were many towels and bed linens. There was a full array of kitchen equipment plus hot cocoa and tea options which were enjoyed!
The flat is close to several metro and bus lines (that and city traffic does add a little noise), markets and a tasty Asian restaurant. Some may need to know that there is a flight of stairs coming up from the metro and then up into the apartment. As it was summer, the blinds in the bedroom helped, but even with open windows in the living/ sofa bed area, Oslo does provide some darkness.
He was very quick and informative in communications. Giving lots of recommendations on top of check in instructions. I would likely stay again and recommend it.