First off, you must watch the extras because there is some really interesting stuff in them, changes to the set, the amount of authenticity etc. The Actors and many of the crew actually gave their time for free or at less than the normal rate because they were so impressed with the script. The director points out some of the stuff that you don't really notice but that adds to the 'feel' of the movie. I was actually prompted to read further about the 'old west' having seen this film.
My only disappointment is that many of the deleted scenes would have actually added a lot to the movie, but pressures on run time meant that they were left out. I do hope that they make a Directors cut of this film, although I don't suppose it's going to happen after 3 years since the original issue.
I bought this along with 'the assassination of Jesse James by the coward, .. etc', which is a truly awful movie in comparison to this one.