I first saw this movie when it was aired on TV, as a two part series. I am, and always have been, a fan of "the other side of the coin" type tales, stories that challenge popular belief. This one always stuck out in my mind as well thought out and imaginative as only Henson can be.
Some scenes can be a little simplistic or almost cheesy, but that is perfectly fine seeing as how this is a family film. The actors are all very good, and the story line itself does a great job of showing the Jack and the Beanstalk story... and then showing "How it really happened."
I actually have a taped-from-tv VHS version of this movie, and was thrilled to find it released on DVD (without commercials every 5 minutes!)
It's great for kids (or the young at heart; I was 18 when I first saw it and I'm 25 now and I STILL love it) and while long, never leaves you bored.