The flat is comfortable and stylish. Once we got over the small hurdle of check-in, everything was okay on that end. There was construction on the outside of the building that began before 8AM, right outside the front bedroom window. Luckily the windows were covered with thick plastic, but it was still unnerving to see a person shape standing outside the window at 7:45 in the morning. We didn't have a lot of time in Oslo, so we got up early anyway and let this slide. I suspect this isn't going to be an on-going issue, so future guests (except those in the very near future) shouldn't have an issue.
The location is great. Far enough from the main bustle of the city that it's relatively quiet and feels very safe, but right on the major bus routes so pretty easy to get around. We had a rental car and were able to park around the street. There's an app you can download for City of Oslo parking (Bil i Oslo), and for the where the flat is zoned, it's not terribly expensive to just leave it on the street and take the bus around. The hostess has left instructions for #RuterBillett (the bus pass) which is a bit weird because nobody really checks it, but you absolutely don't want to be caught without it.
Overall, I'd definitely recommend the spot.