Kevin Costner is a terrible narrator

It is really only bad in the first half or so. Once he gets to live with the Sioux the narrations eases up and it is just a lot of subtitles, which I don't mind at all.

Yes, but his voice is just not up to the task.

Exactly.

I thought it was supposed to be dry, flat and stilted because Dunbar is a soldier, not a writer and was supposed to reflect the writing in the journal, as if he were reading it. Dunbar is not an actor or even a writer. So why would his writing, I.E. "narration" be that of an actor? It was meant to reflect a slightly literate working man.

Like him or not, Kevin Costner's narration in this movie is way easier to listen to than Harrison Ford's in Blade Runner. I mean, I could at least listen to this one 50 more times before I'd have to tell someone to turn it off.

I think I hated Blade Runner for over 15 years because all I knew was Ford's lackluster effort put forth in the US Theatrical Edition. Only in the Final Cut version did I finally enjoy it because they had removed his boring, lunkheaded voiceover.

Point is, narration can be a good thing if done right and if said with the correct emotion to backup what the character is feeling at the time. This time, it happened to work out all fine. At least, for me it did.

I disagree. Narration can be effective in small doses, but to do continuous throughout a movie takes the viewer out of the story. Casino is one of my all time favorite movies, but the constant voice-overs get irritating after a while.