Plus points were Robert Taylor, the before-they-were-famous appearances of several of the cast, and a reasonably fresh plot. (By 1959 virtually every conventional Western theme had been over-repeated.)
But there were several flaws in how the producers depicted the Selah Jennison character, not least the exaggerated head-turning sequences after she'd bought some new clothes. Shortly after her sensational parade through town, she goes skinny-dipping (not uncommon in Westerns) and makes a point of attracting Mackenzie Bovard's attention. Perhaps I could look at the film again to make a particular note of how her attitude to the deputy marshal changed, fluctuated even.
Grilled cell windows facing onto an alleyway feature in many Westerns, but it was only when I was watching "The Hangman" that I realised what a security risk many of these would have been. So wide-spaced were the bars that a hand gun - or even something larger - could have been passed through them to the prisoner.
As others have remarked, the last couple of minutes of the film provided an ending that was none too satisfactory.