We very much enjoyed our stay - the flat is clean and comfortable, and the location is fantastic - so close to everything (especially during the Fringe), but wasn't too loud outside at night. The communication from Sue & Grant was super prompt and helpful.
We did find the wifi to be quite slow (can browse websites, but not stream video - and had to disable my laptop's automated backup so it didn't clog the limited bandwidth), and both beds are a touch short (I'm 6 foot/180 cm tall and had to sleep on an angle), but we were in town to see the Fringe, so these were a long way from dealbreakers. Overall a great stay!