I watched David Lynche's version of Dune this evening.
The film got mediocre ratings and I can see why, but I can't help but feel sympathy for it. I think in the end there's only one major problem and that is that there was simply too much material to cover everything in one film. There was too much exposition, many scenes felt rushed and a lot of (interesting) parts from the books were cut. I think a Dune adaptation really needs to become a two-parter or a trilogy if it wants to cover about everything in a proper way.
On the bright side, some of the special effects were surprisingly good for a 1980's film. Most notably the worms looked great. The acting was also pretty good, but I do think they got some of the actors and costumes wrong. For example, I always imagined Thufir to look like some Arabian guy, but he didn't look like that at all in this film. He didn't even look assassin like and I have the impression they've actually confused Dr Yueh with Thufir.
Anyway, I wouldn't really recommend this film unless you're curious after reading the Dune novel. Personally, I'm hoping for a more modern adaptation someday.