I can see why they changed it: the original title is pretty uncompromising (which I appreciate more in a character than in a title!) and though it's a fair description of what the book's about, it is considerably less appealing. The change of title does emphasise the novel's focus on Salander. Though it's kind of formulaic -- 'The Girl Who [XXX]' sounds more lightweight, more like a children's book.

(Also, GRRR. Why not 'The Woman with the Dragon Tattoo'?)

Do you know if the original Swedish titles of the others have been changed? It makes a nice set in English (and keeps the focus on Salander!)