John's flat is absolutely lovely. It is comfortable, clean, quiet and if you don't mind a walk to the city center, the perfect location. It is conveniently located a block away from a store should you need anything you forgot. His home booklet is absolutely the most thorough I've ever seen: notes on the house (great if you are a foreigner like myself) and local suggestions.
As for the area and getting to the city center: again, it's a hike so bring your walking legs. I walked it every day and enjoyed it. I suggest, as a "shortcut", walking across the Meadows. It's common, well lit at night and i never once, felt unsafe. Edinburgh is a fabulous city, with lots to see and a great hub for day trips.