We stayed at Einar’s house for 4 weeks.
Pros:
Great location, close to shops, restaurants, and transportation (tram and buses).
The kitchen is fully equipped so that you can cook your own meals.
Cons:
There was heavy dust everywhere.
The kitchen had many silverfishes (small insects), which showed up at night.
There was only one bedsheet.
The shared dryer in the basement was out of order (this was not Einar’s fault).
Conclusion:
If you are going to stay for a few days, it is okay and relatively value for money, considering the prices in Oslo.