If you have not seen Planet Earth, you should definitely go see this movie. It shows amazing footage of what goes on in our planet every day in different parts of the world. The cinematography is amazing and it looks good on the big screen.
The only small issue I had was that it looks like the editing needs some work. There were several times during the movie where the transition between scenes was nothing but a silent black screen.
If you have seen Planet Earth, you have already seen a good part of the footage shown in this movie.
I liked the last videos during the credits that show the film makers at work in the wild.
It is a longer than normal movie but so was the first one. Saw it at midnight and enjoyed it a lot. The Joker character was actually very well played by Ledger. Definitely go see one of the best movies of the year.