I really enjoyed staying at Charlie's place. He is a really kind person, with whom you can have the most interesting conversations. He offered to make some breakfast for me (delicious, by the way) and even let me check-out an hour later. There are as well some guides, maps and books about Edinburgh and Scotland for you to enjoy.
The place is a bit far from the city centre (ca. 30 min walking) but easily accesible by bus, and near the Botanic Garden. There is a park on the way to the centre that is very beautiful for a good walk, jogging or cycling. It is a truly enjoyable area, so you won't even mind that it takes a bit longer to get from one place to another (except when you have heavy luggage with you, of course).
All in all, a wonderful place to stay in this amazing city!