Saw this with Jamie at a cinema in Lowestoft. It was good enough to keep me interested for the full three hours.
The film features Oppenheimer a few overlapping worlds; there's the nerdy physicists, the big American war machine, and his home life fringed with Communism. It's fun seeing the army come begging to the scientists, and I could have done with a bit more science, as I think the story of the bomb is a good one. What you get is an awful lot of people being introduced and it takes a while to settle down. Luckily there's a lot of famous cameos to make it easier to remember who's who.
About two-thirds of the way through they succeed in a test-trial of the bomb, which is an exciting moment tinged with a bit of melancholy, as this isn't like landing on the moon, they've made a killing machine. I could have done with more of the politics of dropping the bomb - they mention that Japan was nearly defeated but also that they wouldn't surrender so it's left open whether it was necessary to drop the bombs.
After that the film culminates with two rather boring committee hearings. One in a small grey room is about whether Oppenheimer gets his security clearance renewed. By now its about 1950 and it doesn't seem that important. The other hearing is whether a politician who doesn't like Oppenheimer, gets appointed to the cabinet. Again, very limited interest. These are used as devices to frame parts of Oppenheimer's life, which they do, but to me it's rather clear that Oppenheimer is the good guy here and the politician the bad guy.
There is a bit of ambiguity about whether Oppenheimer really regretted dropping the bomb, or was just saying he did, but he seemed like a decent guy.
The film was OK but not gripping, and it did not make me want to look up the person on Wikipedia afterwards, which is surely the proper test of a Biopic.