Our stay at David's flat was great. Prior to our arrival, David gave us very detailed instructions on how to access the flat and he was super responsive in replying to our email. The flat was very conveniently located yet still quiet and safe, it was clean and fully equipped for a comfortable stay (yay washer and dryer).
The several flights of stairs were not a problem to us but one minor thing was that we were just a little scared of breaking the shower screen (don't hold on to it for support). BTW Edinburgh is beautiful and the people are really nice. Definitely worth a visit.