Some good and not-so-good things.
The best thing about the KM hotel was the invariably cheerful and helpful service desk staff. If there were two of them talking, they immediately stopped and asked how to help me. They also had a very good "Scottish breakfast," with varied foods on the buffet - and they were willing to cook eggs to order in the kitchen. From the web site, I thought I'd be paying extra for breakfast, but it turned out to be included in my total price.
The location was wonderful if you're interested in seeing attractions at the heart of Edinburgh. There are a lot of things within easy walking distance. It was also a quiet neighborhood, which was good, because the windows were far from soundproof - I could easily hear normal street conversations.
The room itself was a mixed bag. It was clean, well-organized, but the very very small and narrow size meant that the (comfortable!) king-size bed was only accessible from one side; the other was jammed up against the wall! Even the "accessible" side only had one foot clearance from the wall, and the location of coat hangers meant that you had to hit your head or duck even on your way to the bed. There were good wall lights for reading in bed, but they were not centered because of the window position, so the side of the bed NOT next to the wall got shortchanged. There was no door on the shower, so it was hard to avoid getting the bathroom floor wet. The sink was microscopic.