Location, location, location. On one of the cutest streets in Edinburgh (people walking down day and night to take pictures for Instagram) and incredibly convenient walk to the Royal Mile and the main tourist attractions while not being right in the midst of it. Lots of shops, cafes and restaurants in the area and nice green space.
Only thing I would say if you are going with a lot of people, the soundproofing between bedrooms/bathroom is not the greatest. I didn't find it to be a problem, but if you're a light sleeper you might be disturbed.