I had a large, rather pretentious ramble about nostalgia and the gross expectations one can have of a remake of a childhood favourite, but instead I'll just keep it short. Walls of text are impressive, but ultimately fairly redundant most of the time if you don't want to spoil something.
It's an OVA about Leo, except this time the jungle is a small artificial island somewhere off the cost of Japan and it's a sci-fi story. One that discusses whether we have the right to claim the status of gods, or if we should just remember that animals or indeed ourselves need to just have some space to run free. Sure the art is different, and there's spots of nifty CG, but it all felt like the sort of story Tezuka would write on a whim, and it's thoroughly enjoyable.
Oh, and if you're one of those fancy modern anime fans who has no Tezuka-related childhood memories, it has Rie Kugimiya playing a pink-haired tsundere character for the 4398th time. No seriously. Though admittedly she's a hummingbird, which is probably the most appropriate species to giver her high-pitched moemoe squeals of frustration.
Go watch it guys. It's better than Hellsing Ultimate 06 was.