Hilde and John Richard are great hosts. They are so helpful in everything and if you are up for it, they will make it possible to squeeze everything possible from Oslo in 24 h. Worked for us!
We loved their apartment. The decor is very balanced and the bedroom where we have stayed has plenty of room and a very very comfy bed, which is great if you walk a lot and want a good night's sleep..
It is very close to city center.