I first saw it as a very young child, maybe when I was six years old? All I can remember from that viewing is that despite all of the weird grotesqueries that Lynch threw in, the thing I was most terrified of was the scene with the Gene Besserit Mother and Paul Atreides with the box, which I just found unbearably tense and freaky as a kid.
I saw it again after reading the first few books in the series, which would have been in college, maybe five years ago. I didn't hate it and certainly thought there were things to admire about it. Some of the flourishes are unique but very weird, like the fucking eyebrows, vagina monsters, and Sting. STING. SO BAD. And also there were those weird pixel fights which must have looked ridiculous even at the time.
The film isn't really a Dune film but a Lynch film of parts of the Dune story. I can only imagine that it would be completely incomprehensible to someone who hasn't read the novel, as it is only incredibly incomprehensible to those who have. Lynch's adaptation has aspects that do work (mainly some of the more cerebral aspects of the novel and sometimes the atmosphere is just right) but never quite come together in a meaningful way. I think Lynch would have been the wrong person to do the film no matter what, but like Grefter, I enjoy ambitious failures. Lynch himself has disowned the film because of studio cuts and interference. I don't think I've seen the longest cut, but somehow I doubt it makes everything come together.
For those who don't know, Lynch turned down directing Return of the Jedi in favor of Dune, which would have been intriguing to say the least. I think Lynch would have done much more in terms of depicting mental anguish and internal conflict than what we got and maybe the Ewoks could also be weird vagina monsters. That probably would have been all wrong too but I'd like to see what he would have come up with.
Also, the first director they got for Dune was Alejandro Jodorowsky, who has made some of the strangest films I've ever seen (exploding frogs!). He wanted to have Salvador Dali as the Emperor (who would have charged $100,000/hour), Orson Welles as Baron Harkonnen and David Carradine (Kung Fu/Kill Bill) as Duke Leto. His concept art makes it look... uh, interesting. From what I've read, it would have been like a fifteen hour acid trip, which isn't too far afield from some of his other films. There's a documentary coming out this year about his version of Dune.
http://www.duneinfo.com/unseen/jodorowsky/http://www.imdb.com/title/tt1935156/ Cid, if you're interested in Lynch's other work, then Blue Velvet, Elephant Man, and Twin Peaks are probably his best and most accessible. The Straight Story doesn't have very many of Lynch's flourishes but it is a good movie about human relationships that is grounded in reality. It is notable for being marketed as "Disney Presents: A David Lynch Film." People also speak highly of Mulholland Drive but that's one that I don't really get.