WFTR
Bill
Like you, I initially blanched at some of the changes between the book and the movie. However, I just finished re-reading all of LoTR including the appendices (first time in about 10 years) and as a result I'm happier with what Jackson did.
For example, I wondered about the wargs in battle with the Rohirrim. Was that in the book? Well, not exactly. The book very clearly states that Saruman kept wargs at Isengard and implies (or I infer) that he would have used them against the Rohirrim in open battles like the Fords of Isen, but not in the battle at Helm's Deep where they wouldn't have been much use.
In another example, in the movie we have the people (civilians) fleeing from Edoras to Helm's Deep. In the book, they go up into the mountains in a totally different place. But then upon re-reading the book, I found that civilians from the western part of Rohan did take refuge in the caves at Helm's Deep. Jackson just compressed things because he couldn't very well split them up and have it make sense.
I carefully read the appendices this time, and there was a lot of material about Aragorn-Arwen-Elrond, including Elrond's being unhappy about Arwen's choice and Arwen following Aragorn in her thoughts, both of which are emphasized more in the movie than the book but at least Jackson didn't invent them from thin air.
I also thought Gollum was done extremely well in the movie. In the book, you often wonder why they didn't just take a sword to the little creep, but in the movie you can see why they would pity him.
So all things considered, I think Jackson's team did a great job. I'm looking forward to the extended DVD of TTT and, of course, RoTK.