I had an excellent stay at Edel apartment; I stayed for two weeks on a work trip and the apartment had everything I needed. Edel was very thoughtful and attentive and was available to contact if I needed any help (which I didn't as her directions were veery clear and picking up the keys was easy).
The apartment is comfortable and spacious, and very close to the centre if Oslo (9min tram or 20min walk). There were some nice cafes in the area and a short walk from the apartment and a Matkroken just around the corner. I recommend Edel and her apartment for your stay in Oslo.