A complex, rich movie that I feel would have gained points if it kept a simpler structure.
I think that Nolan tried to merge different genres into a single movie: historical reconstruction, biografy and legal drama, with some mixed results. While the bio and historical sides are well merged, I feel in the last part the movie transtioned to a legal drama not in a seamless way. Some might find the last part a bit heavy and might feel the need to watch it again to gain full understanding.
The movie is mostly based on flashbacks from Oppenheimer himself, his colleagues and family, which are easy to follow.
Oppenheimer himself portrays himself in his own flashbacks as a typical anti-hero, perennially hunted in his youth by visions on the physical phenomena he was studying (exploding stars, magnetic fields...), and later on by the consequences of his choices. He embarking on difficult political choices being mostly guided by his principles and awareness of dangers of mass destruction weapons.
On the other hand, a more ambiguous and colourful -though overall still positive- persona comes out the flashbacks of his colleagues.
I feel the end result is a very rich, balanced mix of feelings that leaves some ambiguity on his persona, but again, much in a positive light.
Nolan does a superb job framing Oppenheimer, and later Straus, with grandangular lenses to enhance the flow of emotions. The actors were superb to say the least.
For the last part, the director's judgement on Straus was clean cut, voiced by Straus' lawyer. From the ethical PoV, there's a one-sided "the good guy vs the bad guy" kind of interaction, with (what I feel were) somewhat weak motivations behind Straus' actions. The actor, however, does a great job in making everything credible.
In the end, it looks like the director making a trial to Straus as opposed to the mock trial Oppenheimer was subjected to.