This movie was true to the story of Jonah Hex, but it seemed to be missing something. As another reviewer said, it was lacking some character development, so some things seemed flat. Unfortunately, they had so much story to tell, they couldn't fit a lot of character development in it. Perhaps if they'd made a movie out of the prologue in the first 15 minutes of the movie, they could have done a better job of this one. I think that's what made Ironman and Ironman 2 so successful - the first one was mostly development and background. This film needed it to be great. It's sad, I had gone expecting to see the background story of Hex, but they just glossed over it and went straight into the endgame with Turnbull.
I'd say see it, on a cheaper day or matinee.
If you're looking for an action flick with a western setting you won't be disappointed. If you're looking for a Jonah Hex movie, it will be good. If you're looking to learn about Jonah Hex, don't expect too much.