In simple words this place is amazing. Stayed in the apartment for two months and it was a perfect home away from home.
First of all Rasmus is a fantastic host. Only a short message away and would send the odd SMS to check to make sure there where no issues.
Location is excellent, a short walk north of the city center. Plenty of good restaruants and supermarkets within easy access. Although I walk alot, so if you really want to see Oslo, there's plenty of really good restaurants within 20 - 30 minutes stroll.
Apartment is on the top (fifth) floor, so you will need to be mobile. Fortunately Rasmus met me the day I arrived and offered to carry my case up the stairs (thanks for that), but by the end of two months I was certainly a lot fitter :-)
Apartment itself was fantastic, all you need to make yourself at home. Plenty of living area. Bed was comforatble, and the great black-out blinds meant that even on the shortest nights I had no problems sleeping. Internet speed (which I rely on for work, communication and entertainment) was the best I had experienced in all the stays I have had in Norway (7 in the past 16 months). And for all you coffee lovers, well the wall of Nesspresso capuse for the coffee machine will give you a choice of somethign to drink.
I would defintely be putting ths place at the top of my "to stay" list if I get to make any return trips to Oslo. Have no problems recommending this apartment as a top place to stay.