I saw the film first, and while it wasn't a patch on the book when I came to read it there were some great moments in it. I remember Paul's speech to his mother when they're on the desert having escaped the Harkonnens, that was great. I can understand why people who'd read the book first would be disappointed by the film. As an interpretation of the book it's deeply flawed with many things left obscure. Take the moment when Paul drinks the water of life, the film gives no idea what happens other than a sort of transformation has taken place.
All the performances apart from Maclachlen are lacklustre, and the less said about the special effects the better, but for it's (admittedly few) great moments I included it my list.