The check-in experience with Heidi was very simple and we had no problems finding the flat. The flat itself is really lovely, full of art and light. The Frogner neighborhood is very calm, with a great park nearby, but still close to the centre (on foot or by a tram) - definitely a good place to live in Oslo.
Perhaps the only downside was the lack of blinds in the living room - with the summer sun in Norway only setting for a mere few hours, it was quite a challenge to sleep in there. But the actual bedroom has blinds, so it wasn't an issue there. Ideal for two people.