I'm sure everyone is going to pick on me for this (because I'm going against everyone), but honestly I usually don't care how much they deviate from the book, just as long as it has the same theme and the movie is good. The reason being, the movies are never like the book, and I don't treat them, that way. If I want the book, then I'll read the book.
An example of my personal thoughts on the subject is The Talisman is now going to be a mini-series. That's enough for me, I know Spielberg is the executive producer, and it will be long enough to explain the story. If it sucks, oh well, or if they remove a scene from the book, oh well. The real point to me is at least it's getting made. That's the important thing for me, not if they stay true to the book, I just want to see a movie adaptation. (everyone feel free to berate me, lol). Now if were are talking about the Lawnmower Man then I strongly say stay true to the book!
As you can see I'm pretty easy to please