I would be a bit careful about relying on scanraid ratings for human solving. It doesn't seem to correspond too well with actual testing. For example, see Nick Baxter's remarks about the USSC puzzles here (and from direct experience, the 3rd puzzle of the third round was pretty much the toughest one of the bunch).

I agree with this, Scanraid's ratings are sometimes far away from what we could expect. Of course every software will sometimes deliver "strange" scores according to us, but Sudoku Explainer is generally considered more reliable. Anyway I didn't try the tough puzzles yet, so I can't tell about my own experience...