The Scouring was a rather heavy handed "reminder" that evil doesn't need a grand stage. It was also useful to show that underneath Saruman's desire for power there was a petty selfishness that, in the end, bred spite and meaness for their own sakes.
I just finished watching the first two films (getting ready for my visit to the cinema on Thursday) and something irritated me: Gimli shouldn't have been a "comic" figure. There were two times when "dwarf tossing" was referred to. Gimli's pratfalls also seemed out of character. I felt (in the books) that the dwarves could be almost murderous when it came to their dignity being offended.
Also I thought Legolas' "surfing" down the stairs at the ramparts of Helm's Deep was... just plain dumb.
But in the main, I agree; Peter Jackson has done a masterful job and I am moved to read all four books again, right after having seen the final film in PJ's trilogy.