Location is fantastic and we were able to walk to most of the places we wanted to go - Royal Mile, Edinburgh Castle, Arthur's Seat etc. We arrived by train and it is also very close to the Waverley train station.
Check-in was smooth and we didn't have any issues at all thanks to the clear instructions provided. The host is also very responsive and communication was great. The apartment was clean and pleasant, bath towels, basic toiletries and room slippers are provided. There is also a washing machine and we were able to do our laundry on the first day. There are however quite a lot of stairs (~4 flights) to climb to get to the apartment so if you are traveling with old people it might be an issue.