Planet Earth is by far the best documentary on the planet I've ever seen. My kids have been begging to watch it after every episode. THAT'S how you know it's good
I just preordered the DVD series (it will be out in 2 weeks) which is narrated by David Attenborough. According to the reviews I've read, the David Attenborough version is even better because, unlike Sigourney, David actually knows what he's talking about
-- Bill