I had a very nice stay in Oslo in Pom and Tom's apartment. The room is small, but clean and tidy and has everything you might need. You can use the kitchen which is right outside the room, and you have your own bathroom that you share with other guests if there are any, otherwise you have it to yourself.
Pom and Tom are very friendly and welcoming, they gave me advice on what to see and where to go and even did my laundry for me one time. I especially appreciated the city bike card they lent me so I could use the city bikes free of charge. I would absolutely recommend getting around on bike by the way, it's a great way to see the city.
The apartment is in a nice part of town with plenty of restaurants and cafés close-by, and the hip district of Grünerlokka with even more cafés and vintage shops only a 10 minute walk away.