I got this movie from eBay, and brought it in to watch with some of my students during our open studio session yesterday, and man-oh-man, was I impressed.
First off, though the film's plot has the same overlookable shortcomings that similar films like The Killers or Leone's Spaghetti Westerns, the directing is top-notch. There are lots of great stylistic choices that are consistent - the Good always framed in a way that he is bathed in light, the Bad generally introduced into each scene with a from-the-front shot lit from above, the Weird shot from behind so that we identify most with him, the Japanese are never seen walking, always riding (hinting, I think, at the exploitation of the subjugated Koreans and Chinese)... the film has some of the best color decisions I've ever seen made, and wonderful compositions. Some of the shots are mind-bogglingly complex, and it's a real treat as a film.
From a subject matter standpoint, you couldn't ask for better. Mongolian gangs, refugee shantytowns, trains, opium dens, motorcycle/horses/jeeps/artillery chase scenes, well-orchestrated gunfights galore, Japanese cavalry, treasure maps, etc. Great scenery that should give you plenty of ideas, as well as great character archetypes (the guy with the hammer, for example, or the flail-wielding Mongolian Chieftan, or the duplicitous Opium-Den proprietor).