Slow West nearly lives up to its name, but through some command performances--a pointed screenplay, strong cast performances, and fits of violence that are terribly bloody --the western shows its "stuff". Whether you will enjoy it's story is another issue all together.
Slow West will not always hold your focused attention, as the screenplay (by director John Maclean) likes to let its characters chatter on endlessly... the first half was at risk from bits of irregularity. The scenes aren't always good, but they are simple and somewhat mesmerizing... and, it could be that that Maclean does not really give a hoot whether they do or not.
The story seems to understand and embrace that it's an underdog in a genre that far too few people care about because Slow West is especially aware and live up to it. It does not have lots of flashiness like of any one of the many Clint Eastwood westerns; the bravado of the movie 3:10 to Yuma, or the big characters we're used to - though do not tell Michael Fassbender that, while standing too close.
Slow West isn't a film everyone will enjoy, but not every film must appease the masses.