It's on the Images Journal list of 30 Great Westerns. DVD Talk says it "holds a special place at the end of the 'innocent' era of American Westerns". The Western Review calls it "a stylish and well paced—if awkwardly plotted—tale of intrigue and betrayal." The book 1001 Movies You Must See Before You Die calls it
a taut, tragic tale with a memorable hit theme song... and Mann's trademarked sense of the way desperate and obsessed men relate to each other and of the dangerous landscape that emphasizes their extreme psychological states.It gets a score of 100% from Rotten Tomatoes.
Other Westerns I've seen are listed here.