You can watch it online tinted and with a new score:
Slant Magazine calls it "John Ford's first official epic, as well as his breakthrough hit." Variety says, "John Ford, who directs, puts his story over on the screen with a lot of punch." Images Journal lists it as one of the 30 Best Westerns and notes that
The Iron Horse contains many of the themes that Ford would explore in his sound-era Westerns. One of the main themes centers upon the men who sacrificed their lives in order to help bring civilization to the wilderness.
MSN has an overview. It gets an 83% rating at Rotten Tomatoes.