You can pay $5 to watch it online or just buy the Criterion edition like I did.
Moria has a review and gives it 4 stars. Variety praises the casting. DVDTalk reviews the Criterion release and says of the film,
The supernatural part of Onibaba is secondary to director Shindo's main theme - the human debasement of war. The two women make a ghoulish living in isolation, with survival their only remaining value. It's a harsh world where everyone must make do on their own.The New York Times opens its review with this:
SELF-PRESERVATION and sex in a primitive society made desperate and bestial by war are the raw materials out of which Kaneto Shindo has conjured up "Onibaba" ("The Demon")MUBI has some information. Rotten Tomatoes calls it "A landmark in fantasy cinema".