The apartment is just as advertised —clean, comfortable (although the bed in the main bedroom is very squeaky and a little cambered, so you feel like you're rolling toward one edge or the other!). The kitchen is very well stocked and the bathroom is modern, with a powerful shower.
The best thing about the apartment is its location, right on the Royal Mile, just a short walk from pretty much everywhere, including Waverley train station.
Callum communicated very well. We never met him, but he was very clear and prompt with replies to questions.