The flat is amazing: it's bright, sunny, spacious, and located on (in my opinion) one of the very best streets in the best neighborhood in Berlin, Prenzlauer Berg. It's on the top floor of a walk-up (lots of stairs, which is typical for buildings of this type); the front room overlooks the main street and the bedroom is toward the back, looking over an interior courtyard. Perhaps because of the high floor, it's remarkably quiet - an unexpected surprise. The flat is also very close to trams and trains for easy travel around town.
Julia was super helpful and quickly responsive; in particular, she provided a comprehensive list of local restaurants upon request and met us in person to show us around. We'd return in a heartbeat.