The new film version of V for Vendetta takes a coherent, if complex, set of narratives, and excises most of the sense but none of the style. It's a very sleekly done movie, and like many of the recent comic book adaptations borrows freely from the panels of the original work in staging scenes.
Aside from the ham-handed insertion of a conspiracy theory involving pharmaceutical companies, which disrupted the internal timeline and altered the villains' motivations,* there were some tweaks here and there that shifted one of the important themes of the graphic novel entirely out of the picture. In doing so, it betrayed the underlying work in a serious way. (Spoilers for both the graphic novel and film follow.)
In the novel, Evey is an impoverished prostitute with a day job at a munitions plant, not a middle class television employee late for a date with one of the network's stars. She has a sexual relationship with a thug after she is abandoned by V. By whitewashing Evey's character, the film makes her easier for us to relate to, but it also whitewashes the sins of the society in which she lives, and it keeps her pure for her "true love," V, who never consummates the attraction. Apparently we can be expected to identify with a terrorist girl, but not a terrorist girl who has sex. By transforming Gordon's character from rough trade to chaste homosexual, all opportunity for Evey to fall from grace is removed.
Other subplots from the comics dealing with the downward slide of a Party member's widow and the Evita-like aspirations of one of the leadership were neatly (and perhaps necessarily) excised. But that means that the seedy underbelly of Norsefire England, in which women can only rise to power or remain respectable through their men, was obliterated. Instead we have the virginal Evey, pure and deadly as Joan of Arc. Neutering Evey and deleting the other female characters meant refusing to deal with fascism's impact on women. Moore's original novel was sensitive to this issue. I cannot understand why the Wachowskis were not.
* If Norsefire only came to power after the post-St.Mary's virus riots, how did they have the authority to put homosexuals and non-whites in the camps where the virus was engineered months before?
UPDATE: PG agrees that the changes made to emphasize the Evey/V relationship were negative.