We really enjoyed the movie. I didn't even mind Matt Damon very much. I liked the Jeff Bridges version of Rooster Cogburn, and the little girl who played Matty (Hailee Steinfeld) was astonishing. She'll be worth watching in the future.
But what struck both Georgia and I was the stilted, formal speaking style that was maintained pretty consistently throughout the movie, even by the scummy bad guys. I don't really know if that's way people actually spoke in America in that period, but it's certainly the way old books were written, and I suspect that they may have actually done some pretty good research on this. Or not, maybe they're just putting us on, but it worked, and helped make the illusion of the period.