Totally worth it.
Based on actual events, Matewan relates the events leading up to the Battle of Matewan, when the coal company's gun thugs came in to massacre the striking miners and found the miners fully prepared to shoot back. The movie stops there, though an epilogue hints at the increased violence poured down on the miners (by both the coal and the state) for daring to fight back.
It's a powerful examination of the struggle to create unions in this country -- who paid, how they paid, how much they paid -- and who the true enemies are. It also shows, very nicely, how they work (successfully) to set us against one another.
Watch it, even if you have to buy it.