This is a really interesting sequence. where good changes and bad changes of P.J. are very close to each other.
One of my favourite only-movie scenes is the dialogue between Gríma and Éowyn. That is no witless worm we meet here: It is an intelligent, though unscrupulous (not completely unscrupulous, as we will see later) man who chose his loyalties wrong. For a second we are made believe that Éowyn could comply.
I took a closer look on "Gríma's thugs" this time. There are five of them that lurk at the side when the four approach Théoden. And there are exactly five unconscious bodies on the floor after the fight. Some of them don't even look rohirric but rather dunlendic. How did Gríma import those?
I don't think we have to fear for the loyalty of the majority.
And now there's the exorcism...
Actually I liked that Jackson made Saruman's hold over Théoden stronger, but as so many other times, he simply overdid it.
Did you notice how Gandalf reacts after the King's decision? He leaves Meduseld for the stables, ranting over the decision in front of all the people. Very decent, Greyhame.