This is a super little flat. Lovely and quiet but also in one of the best (and liveliest) parts of the city as it's just one minute from Grassmarket. My husband and I stayed for a long weekend at the end of July, David was very helpful and offered assistance and recommendations wherever possible, he'd also left us a small supply of cupboard essentials so that when we arrived close to midnight on a Thursday night we could help ourselves to a cup of tea and a biscuit! The flat is a the top of a small residential block - there's no stairs but it's not too far to the top. Once at the top you have the most superb, uninterrupted view of the castle, it really is worth it just for that!
To summarise, a fabulous little flat, super host, excellent location. We would stay again :)