Benedict Cumberbatch and Keira Knightley both turn in brilliant performances in difficult roles. Graham Moore's script relies significantly on the relationship between their characters. Cumberbatch's Turing is an unrepentant ass, with significant deficits in social skills, afflicted with a (probably justified) sense of his own brilliance and importance. Knightley's Joan Clarke is a woman who may well be as smart or smarter than Turing but whose gender leads her to be held back both in academic and professional circles. She battles the sexism and misogyny of her era in this film and the script gives her some good screen time to rip into that.
The film has what I call "the Titanic problem" - you know how it's going to end. The ship is going to sink; Alan Turing is going to be prosecuted for being a homosexual and take his life rather than endure more of the hormonal poisons meted out to "cure" him. Like Titanic this film chooses to deal with that by telling things as flashbacks from the end-point. It's not so much a question of what's going to happen - it's how did we get here. There's some initial confusion as the flashbacks go from 1951 to 1939 and there's not a lot of change in people's appearances or the scenery but it's soon easily sorted out.
This film is totally worth seeing if you have any interest in Turing, code-breaking, or WWII. It's also worth seeing as an illustration of how things have changed, or not changed, in the past half century.