We stayed in Katias appartment with 4 persons for 7 days and enjoyed every single day! Katias description of the appartment are absolutely accurate so we believe there is nothing to add here.
Although we never met in person, communication with Katia was always very easy and helpful (in particular the hint, not to travel into town by car... - public transportion is easy to use in Stockholm with the next bus stop being just around the corner and the next underground station also being nearby).
Unfortunately, the weather was not too nice during our stay so that we could never really use the great rooftop terrasse, however, the more appreciated the cosiness of the appartment after returning home.
All-in-all, we can only recommend Katias place to everybody interested to explore beautiful Stockholm and looking for a centrally located appartment with a great atmosphere!