I enjoyed the film but was irritated at the many inaccuracies. Despite these lapses, it's a colourful film and Cumberbatch and Knightley are excellent performers.

A bit spelt out for an American(?) audience, who are ignorant of British history? Or else just the ignorant. All made easy-peasy for those who didn't know that Britain fought in the 2nd World war, and was bombed. Or that women were rarely supposed to be in important posts. Key the scene where Keira Knightly (all uglied up with thick eyebrows) is told she can't enter the candidates room because the secretaries are supposed to go elsewhere.
Still, well acted and I suppose the melodrama has to come from somewhere to keep up the interest when all that seems to be happening is a problem with a big whirly machine that won't behave. So brothers on convoys that are probably being torpedoed are invented to point out the pressures.
Good stuff on the whole.

I went in with no expectations, but its a well directed film with plenty of tongue in the cheek humour and a pretty good script... never a dull moment. Cumberbatch is indeed superb, as is Mark Strong as a particularly slick but evil MI6 man.