Goodish, but not great. Excessively long, at over three hours. Lacks focus, dwelling too much on minor details and irrelevant sub- plots. It could easily have been cut down to two hours, and been tighter, punchier and just as character-centric.
I am not a fan of Kevin Costner, and this movie didn't help that impression. He doesn't do Wyatt Earp much justice - trying to act the hero by being cool and calm, but just coming across as solemn, aloof and boring.
This said, the cinematography and scenery are great. Dennis Quaid's portrayal of Doc Holliday is something to behold.
The remainder of the cast is pretty amazing for the names involved, some of which weren't stars yet and/or had very minor roles - Gene Hackman, Mark Harmon, Bill Pullman, Michael Madsen, Jeff Fahey, Isabella Rossellini, Tom Sizemore, Mare Winningham, Tea Leoni.
So much potential wasted.