A truly romantic apartment, really comfortable and well situated. The castle is at about 5-10 min by walk and you can reach every touristy parts of the city in 30 min by walk. Even Holyrood Palace ! We did not use public transport except for travel to / from airport.
As it is located in Grassmarket, there are a lot of pubs and restaurants (try Le Petit Paris, they make great meals).
Susan had answer to all of our questions quickly and it was helpful in order to organize our trip.
The apartment was equipped with all the standard equipments and a good kitchen.