For one example, there's Cecilia Vanger. In the book, Blomkvist sleeps with her, on a semi-regular basis, until she runs into the inevitable fact of his long-term affair with Erika Berger. In the movie, she expresses interest but he declines, apparently because she is a suspect in the murder he is investigating.

This is a reasonable qualm, and it indicates that Blomkvist (in the movie) has better judgment than Blomkvist (in the book). But there's also the fact that Cecilia Vanger is clearly emotionally troubled (at least in the book), and his sleeping with her casts his later relationship with Salander in a different light, as if he has a particular attraction to emotionally troubled women (from whom he will then keep a certain emotional distance because there is always Berger).

In the scene in the movie where Cecilia Vanger indicates her interest, I half-expected Blomkvist to say, "I'd love to, but this is only a two-hour movie! Hey, meet me after the credits."

For another example, in the book Blomkvist's daughter pops in to visit him for no good reason. He's clearly not that interested in her (and neither is Larsson), but she appears just long enough to give her father a key piece of evidence in the case, and then she leaves. Deus ex machina, and so clumsy that it's actually rather endearing. But in the movie the daughter doesn't appear, and Salander comes up with the key piece of information. Which is better in every way.

(Hey, spoilers coming. I warned you.)

There is one thing I really miss in the movie, though. There's a scene, after Martin is dead, when Frode, the lawyer, comes to visit Blomkvist and Salander, conveying a message from Henrik Vanger that the case is over. The book will not be written, and the story will not be told.

Until this moment, these three people (Blomkvist, Salander, and Vanger) had the same goal, to find out what happened to Harriet Vanger. But suddenly, the mystery solved, they have different goals (because they really had different goals all along, but they didn't realize it).

Vanger wants what is best for the Vanger family and the Vanger company, which is for nobody to ever find out what happened. Blomkvist, the crusading reporter, wants the story to get out, but he knows that he is being bought and has to do what Henrik Vanger wants. Salander can't be bought (as she points out in a wonderful moment when Frode forgot she was even in the room because as usual she was more absorbed with her laptop than anything else), but she also realized that there will be no gain, and more women will be hurt, if this comes out.

This is a wonderful scene, including the additional message that Vanger still considers Blomkvist his friend (which is clearly true, within the confines of an employer-employee relationship), because it reflects a lot of knowledge of how people think and act. There are disadvantages in having a novel written by a journalist, but there are moments when it becomes a good thing. And it's also interesting because, although Blomkvist has appeared throughout to be a wish-fulfillment character for the author (both are middle-aged crusading journalists, but Blomkvist is also inexplicably attractive to pretty much every woman he meets), he is not the moral center of the book. Salander is. She is incorruptible, she is clear on right and wrong (she is similar to Rorschach in many ways, but with very different politics), and in this scene Larsson is obviously in agreement with her.