As an adaptation of Dune, the novel, it definitely sucks.
As a coherent story on its own merits, it also kinda sucks.
As an ostentatious display of gorgeous set design, costumes, imaginative ships, nutty visuals, eccentric ideas, and some of the hammiest over-the-top acting I've ever seen in a movie, it's a lot of fun, which is why I love it.
Edit: is there really an unreleased full Brian Eno soundtrack to the movie? He has one terrific track on there but I didn't know he'd supposedly done more.