Christin's apartment was the perfect place for us to stay in Oslo. The apartment itself is lovely - spacious and welcoming, and beautifully decorated (loads of books, and a great clock collection!).
The kitchen had everything we needed, the bathroom too, and we slept well in the beds.
The apartment is located very close to tram stops so getting around was very simple, and there's plenty to do in Grünerløkka itself, or within easy walking distance (among others, Popsenteret is well worth a visit). The Kiwi and Bunnpris supermarkets are great for picking up provisions.
Christin was so helpful in providing information and quick responses to messages, and the check-in and check-out processes were very simple. (One tip for getting into the building: the lock on the external door is a bit fiddly, but persist and it will open!)
We'd definitely want to stay again if we make it back to Oslo!