I had a wonderful month at Rachel's! The photos are perfectly accurate -- it's a lovely, clean studio with a king sized bed, a modern kitchen, and a spacious bathroom. Rachel was the perfect host: quite literally responded to me within 10 minutes upon every contact, and frequently checked in to make sure everything was going well.
The flat is perfectly located for tourism: it's a block from the castle, on the Royal Mile, and thus on the central boundary of the city, between Old and New Towns. It's on a slightly busy street, so if you are a very light sleeper there may be an issue with the traffic noises, but was completely fine for me.
I can't recommend the place more highly!