I have only seen the SciFi Channel miniseries and thought it was one of the most boring pieces of film I've ever seen. I'm not even sure I finished it. I kept falling asleep.
The miniseries has to be approached as a stage play that was filmed. If you look at it that way, it's actually pretty good, particularly if you've read the book and realize how closely they stuck to it.
But I'll agree it can drag in places. As a television production, Children of Dune was much better, although some of the abridgments confuse the story in places.