Hi Cormorant,
the Great Edinburgh Run is superb - I ran it for the first time last May. The route itself is fantastic, and it looks pretty spot on from your entry on mapometer. Last year, they secured the finish within the grounds of Holyrood palace, so having come down the royal mile you head towards abbeyhill, then cut into the palace and finished in there.
You've nailed the route at the national gallery too.
Not sure if they managed to secure that finish again this year - shame if they didn't.
I won't be making it this year as I'm doing the Loch Ness Marathon on the same day - gutted they moved the edinburgh run from may to october! not sure of the reasoning for that.
Take it easy on the hill out of holyrood park - its a long one, but after that its a great and fast route.