Less is more. This should be tattooed on the foreheads of those involved with this, which starts off brilliantly, but by the end has become a blunt instrument and a ragbag of cute bumper-sticker philosophy, like "People should not be afraid of their governments. Governments should be afraid of their people." Works well on a T-shirt; less well when intoned with utmost seriousness by a man in a Guy Fawkes mask, I find. Do appreciate the additional frisson recent history gives this; making a film where the hero is, effectively, a terrorist is now a somewhat brave statement. V (Weaving, his face never seen) takes on the fascist regime running the UK; he rescues Evey (Portman) from the police, but when she returns the favour, he is forced to take her under his wing as he works towards his ultimate goal of bringing down the government.
Graphic novel author Alan Moore removed his name from the adaptation of his work, making him 3-for-3 there. I believe the main problem was V becoming a generally heroic figure; in the original, the reader was left to decide uncomfortably between fascism or anarchy. Moore described this as "a thwarted and frustrated and largely impotent American liberal fantasy of someone with American liberal values standing up against a state run by neoconservatives - which is not what the comic V for Vendetta was about." Any subtlety is absent here, replaced by black and white hats, with little doubt or room for debate. It's clear that John Hurt's dictator = Dubya, not the parallel Moore intended, writing during the height of Thatcherism, and he criticized the makers for making an American fable, not set in America.
On its own terms, purely as a film, the Evey/V relationship smells of a sop to focus groups, despite performances which are solid enough to avoid grating. Rea's policeman is perhaps most interesting there, a man torn between a duty to catch V and the unpleasant data regarding his government employers which he uncovers. Anyone expecting action, a reasonable assumption from the trailer, will probably be disappointed by the relatively small amount, though it's well-staged. The worst mis-step is, however, a faithful recreation from Moore's work where the imprisoned Evey finds a letter by a previous prisoner. This embarrassingly-earnest sequence stalled the film entirely for me, and it never got started again. The overall result is disappointing: just another Hollywood flick, feeling more like the product of someone who wants to play with subversiveness, rather than genuine revolution.