One of the best TV series I've seen
And I say this as a young non-american who has seen most of the modern highest rated TV shows like Breaking Bad, True Detective and some old ones like Twilight Zone, Star Trek and Twin Peaks. I mention this not to be mistaken for a nostalgic old guy.
I only recently found it on TV and I must say I'm impressed. Most of the episodes are movie-worthy with their stories and I especially like the complex aproach to characterization not typical for westerns of that era. Characters are almost never one-dimensional villains or heroes and often evolve during the course of an episode.
Some of the episodes serve as a comic relief though so don't expect each and every one of them to be perfect. I also didn't catch all the episodes from the start, only started watching the later seasons.
Definitely recommend this if you're a fan of classic western, but I like it even though I'm not (spaghetti is more my taste) and so may you.