Location is good in terms of seeing the sites as its directly on the Royal Mile. However, it is noisy at night, both on the Royal Mile side and and side street that the hotel overlooks so if you are not going to party, make sure you get a room on the quiet side.
If you are used to a high standard of modern hotel from Radisson SAS be aware that this one is not the usual standard as it is housed in a previously existing hotel that they have taken over, so not purpose built - small rooms (but fine, serviceable)
Service on reception - depends on who you get. Several were perfectly good and helpful, but one woman on reception, can't remember her name, eastern european I think, couldn't be bothered to do more than the minimum and either through lack of language skills, or lack or personality, came across as rude.
Bar was quite nice for a late night drink
Breakfast was the usual buffet but housed in a dank and dark basement room - bit depressing.
All in all, I'd say not worth the money - if you are on a budget, try the holiday inn express - either of the two has rooms just as good or better and are half the price usually. If you have more to spend, go to the glasshouse for modern (get a terrace room) or the Balmoral for traditional (right next to the railway station and very central).