I spent 28 days in Julia's flat and can't say enough about her and her co-host/husband, Casper. Casper met me at the flat, showed me around and was immediately responsive to every question I had.
The flat is located in a very central, very historic neighborhood. Lots of cafes, bars (and, just diagonally across the street, the Sant Petri bakery, which had the most incredible pastries; I went there nearly every day).
About those bars: The flat is located close to the university, so there are a lot of young people out and about sometimes till quite late. And, being young people, they make some noise. Personally, it didn't bother me much, particularly since the bedroom is in the rear of the flat and was, for me, more than quiet enough for sleeping.
I would give this flat a 4.8 out of 5, and those .2 demerits were for two things: 1) I found the Wi-Fi lacking. It was fine for working, which I did a lot of while I was there, but downloading was very slow, and streaming films, etc., was nearly impossible--constant buffering and freezing. 2) The flat could use a workstation and a proper desk chair with back support. There's only a picnic-style table with wooden slat benches, which was murder on my back after a couple hours on my laptop.
Overall, though, I had a terrific time in the flat, and in Copenhagen.
Thanks, Julia and Casper!