We were traveling as a family of 6 from the US and the location is perfect - just off the Royal Mile halfway between Edinburgh Castle and Holyrood Palace. The flat is nicely decorated, the beds are comfortable, the bathrooms are updated. The washer/dryer combo machine is very small (I had the same type of machine in our London flat so I assume this is par for the course) so you can do only very small amounts at a time and drying takes a while. If you have lots of laundry to do it may be worthwhile to just drop off at a laundry service. The wood floors and doors are very creaky so if you have a light sleeper, bring white noise of some sort. Those are minor complaints and we would definitely stay here again if back in Edinburgh! Everything is within walking distance - Waverley Station, Arthur's Seat, Princes Street Gardens, Edinburgh Castle, Holyrood Palace, Parliament House, grocery store, museums,etc... the Royal Mile is very touristy and you pay tourist prices but the location just couldn't be better for walking everywhere. A couple of restaurant tips - we had light breakfast in the flat most mornings but tried Larder once (just up the street from the flat) and the Scotch pancakes with lemon thyme syrup are AMAZING; Oink serves yummy shredded pork sandwiches, crisps and a drink for 6 pounds and is on the way to Arthur's Seat - you don't want to hike up hungry!
Colin was quick to respond to any communication, check-in instructions were clear, and follow-up from the management company was polite and appreciated.