How others will see it. It is a cartoon, a necessity in 1978 since the protagonists are rabbits. The target audience is Anglo intellectuals and not children. The film is faithful to Richard Adams' bestseller novel. Those who grasp the film's philosphical and political messages may be enlightened and appreciative (more on this later). Those who must see it as cartoon will find it uncomfortable, and perhaps too scary or intense at times for young children.
How I felt about it. Hazel is just looking for a place to live in peace, freedom, and safety, along with his loyal friends and allies. But the rabbits and their travails are clearly an allegory, much like George Orwell's Animal Farm isn't really about farm animals.
The allegory is chiefly political, and partly philosphical and spiritual. Hazel encounters through four warrens, including one of his own making. The third warren, with the bellicose general, is a regimented military dictatorship. The first one is also a dictatorship, although more freedoms are allowed, and less punishment is meted out. The second warren is purely socialistic. No one works, there is no defense, a boundy is provided for, and the rabbits meekly accept whatever ill end will befall them. Hazel is the strategist, Fiver is the visionary, Bigelow is the military. The democracy elects leaders, who appoint advisors.
So, in order, we have Republic, Socialist, Communist, and Democratic warrens. Even in the democratic government, there are orders given and followed, but these are always for the long term good of the community. Watership Down offers religious insight as well. Predators exist to control populations, which if let alone, would end in removal of resources (starvation.) Death can be brutal, but it can also be graceful, even peaceful. The black rabbit comes for everyone, sooner or later.
At least, that is my interpretation, and you are welcome to your own. If your interpretation is that this is just an interesting story about rabbits, I suggest you are missing something, but perhaps that is better than making sweeping conclusions out of singular events.
The British interest in this production is evident by the legendary actors who contribute their voices. John Hurt, Ralph Richardson, Denholm Elliott. It's hardly a who's who of British theater, but it's credible, and the class shows through in the film as well. A warning to dog lovers, however. Dogs don't come off very well. They're stupid, noisy, and destructive. At least, that's how cartoon rabbits see them.