Pretty good. I'd give it 4 out of 5. If you're looking for non-stop action, this ain't your thing. The shootout is anti-climatic. It's more of a character study/history type thing without being anything like a documentary. It's not Hatfields and McCoys. The thing that jumped out at me was how subdued and gentlemanly Hamer and his sidekick were. Probably pretty realistic.
I liked the movie a lot. tough, understated protagonists. real depression. real guns. interaction between Hamer and Barrow Sr. was good even if not historical. real politics.
Damn lucky none of the good guys got shot in a melee like that.
And at the end, the realization of what media and celebrity can add up to.