If you look for centrally located, convenient to main attractions, quick and easy to and from airport and yet not expensive, this is the place you should go for.
In addition to the beautiful and conveniently located apartment, the host, Yamile and her husband are the best host so far I have met. They respond promptly, help you out whenever you need, even my personal request not related to the apartment!
I will not hesitate to stay with them again and recommend to anyone traveling to oslo!