It's got an incomprehensible plot that mostly consists of dry, monotone narration and overdramatic scenes you can't understand set to some sort of rock opera.
In other words, so bad it's good.
Edit: I don't mind plots being incomprehensible (I liked Mulholland Drive) but in Dune it's not even done that well, and you sorta get the impression that it was trying to make sense, but failed.
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http://img228.imageshack.us/img228/7267/chillsloth.gif
It's hard work living as a sloth, but he finds time to relax.