Mark's apartment is a really nice place and ideally located in the main street of Edinburgh. It's easily and quickly reachable from the Waverley Bridge (about 5-7 minutes).
The room was clean and neat and had everything to offer: wifi, towels, hair-dryer, guide books and a big comfortable double-bed (the most important!). And it is calm because the windows open on a nice inner square.
Although I only stayed one night at his place, I could talk to Mark who was welcoming and gave me some useful tips about what to see and do. He was easy-going and we could use his apartment as if it was ours.
Besides we kept in touch regularly and he always replied very quickly.
I would strongly recommend his place to anyone visiting Edinburgh!