I had a great stay at Kirsti's place. The apartment itself was very stylish and located in a quiet residential neighbourhood of Oslo (with a friendly cat living in the house upstairs as a bonus). The apartment itself is located in the basement of Kirsti's house but is very private: you share a main entranceway with the house above but the apartment itself has its own front door.
The apartment was perfectly situated to hop in and out of the city centre, with bus 37 around the corner (which heads to the centre), and a bus to e.g. Vigeland Park and the museums on Bygdøy a short walk away. Most places are about a 15-20 minute bus ride away, but it's actually quite a pleasant 30 minute walk into the city centre as well.
Simultaneously because the apartment is located in such a lovely, quiet, and green part of Oslo, it's nice to come home to at the end of the day and get a bit of peace and quiet.
The apartment really has everything you could need for both shorter and longer stays, including a well-stocked little kitchen. There's a range of smaller and larger supermarkets nearby, so it's easy to shop for groceries in a range of budgets.
My only point of advice would be to bring an eye-mask if you are a light sleeper and visiting in the summer: the curtains in the bedroom let in quite a bit of light during the long summer nights (and early mornings) in Norway. But this certainly didn't put a damper on my stay.
All in all, I can wholeheartedly recommend Kirsti's place.