I spent two weeks in Jo's studio and was very satisfied. The bed is comfortable (if you dont mind climbing the stairs), the bathroom is modern and spotless and the kitchen corner has what you need for some simple meals. I really appreciated finding some cereals, juice, coffee/tea, etc. in the cupboards when arriving, since I didn't have time for grocery shopping when arriving.
The location is fantastic, right behind the castle, close to Frognerveien with all the shops and restaurants you need - and still very quiet.
Thanks, Jo, I'll happily recommend this place.