My wife and I thoroughly enjoyed staying at this flat for our 11 night trip to Edinburgh (for The Open).
The flat was located in a very nice area of New Town, just 3 blocks from Princes Street and a 10-15 minute walk to the Royal Mile and Edinburgh Castle. Also very close walk to Waverly Station and the tram to/from the Airport. overall, great location from which to explore Edinburgh...no need for a vehicle while in town.
The flat is very comfortably-sized for a couple and can easily manage a third person. Beyond that, it might get a little bit tight. It was quite clean and we spent half of our evenings at home, just relaxing after being out and about. The bed and couch were very comfortable. The kitchen was well-equipped (although note the fridge is a half-size one).
Thistle Street is close to a number of restaurants and public houses (including Inspector Rebus' favourite, the Oxford). Rose Street is just two blocks away and has a number of nice places and is a pedestrian-only walkway for 4 blocks or so.
The Street was a bit noisy in the evenings with the windows open, but with them shut and the wooden shutters closed, quite reasonably quiet for sleeping.
We rented a car for 4 days during our trip and found we were able to park on Thistle St after 6:30 pm each night (which is when parking is free till 8:30 am the next morning).
Communication with Dunc & Dee was great, with quick responses to our questions.
I would very much recommend the unit as a central base from which to explore Edinburgh and the surrounding region.