If you're traveling with young kids, this is a great place to stay! From the high chair and crib, to a loaner stroller and training potty, the set-up is great for parents. For the kids, there's a neat little corner all set up for them including books, crayons, rubber stamps, and paper. There's stuff like puzzles for the older kids, but I was with a toddler, the books and colors were good. I think I counted around 80 stairs or so from the street level to the flat, so go in with your eyes open and good shoes. My toddler walked them twice a day, so it's do-able even at the end of along day of walking the city.
The flat was clean and comfortable and even though the bedrooms are right on the Royal Mile there was no annoying street noise. Great base to walk the Royal Mile or to explore further.
There's an independent cafe across the street called Deacon Brodie's that was our morning base all three mornings we were there - great food, good service, friendly staff. At the bottom of a set of stairs from the courtyard/close is an independent restaurant called Makar's Mash Bar. Best meal I had in the Old Town hands down. Skip the industrial pubs along the Royal Mile though...it was all bland and the menus were nearly identical. There's good food to be had within an easy walk of the flat.