I have seen all the nominees and believe Imitation Game should win. Boyhood will probably win just because of the scope of the project and how well it was pulled off. American Sniper is great, and deserves the nomination, but it is not going to win and it should not win, in my opinion.
I'm a big fan of Alan Turing. He's a very significant figure in the history of computer science. However, for most of the people who know of him, and admire him, his overwhelming importance is simply his secret perversion.