I'm putting the negatives at the top because I agree with the good stuff other guests have written. The neighbors in the building are very loud. I stayed here many weeks because of work in Oslo, and even on nights before weekdays and outside of the quiet hours there could be parties. Incredibly loud music. I could hear everything down in the basement where the bedroom is. They got some crazy friends who would just scream at each other.
On non-party nights other neighbors would listen to music with a strong base and watch loud movies until the early AMs. The first couple of nights they would turn it down when I banged the wall. After some nights they stopped responding and kept it up.
I can't tell the frequency of the parties since I would leave Oslo most weekends. The host seemed not able to do anything about it.
Positives: Nice neighborhood with a lot of outdoor seating. I loved all the close-by parks. If you feel like being trendy this is a place for you.
To be clear: You might really like this place. Either you are not like me and not easily disturbed when going to sleep, or you stay over a non-party period. The place is well decorated and it has most things you might want for a shorter stay. If you eat out a lot, it's great for long term too.