It's online at googlevideo:
and at the Internet Archive.
Vincent Price is the linchpin of the entire affair. Through his skill and will, the production is graced with believability and pathos.
1000 Misspent Hours praises Vincent Price's performance while panning everything else. Moria has a review that points out that this is the only film version that maintains the novel's ending. Stomp Tokyo says the film "supplies some powerful imagery".
5/30/2009: Vault of Horror has a review which praises the film and says, "if you want to see the original undead apocalypse movie, this is where you need to go."