Right. So.
This is by no means a perfect movie, nor is it a perfect rendition of the book. But most of the changes are understandable or ended up not bothering me as much as I expected.
Some of the casting choice have been criticized for stupid political reasons. Liet Keynes being a black woman instead of a white guy has zero impact on anything. The book was written in the '60s, and it shows; that both major cultures (Imperial and Fremen) are based on/heavily influenced by patriarchal societies on Earth (feudal/Christian with some Muslim influence for one, Buddhist-Muslim for the other) is a valid choice but it does mean in modern views the story suffers. Women were given power but aren't in the spotlight in the book(s) and this mostly remains true. Liet being female might make it harder to swallow for some that she would gain the influence she has etc etc, but that's only an issue if a) you include a lot more info than is presented in the movie (and book - you'd need info from the prequels and sequels) , and b) if you think patriarchal views now are the same as those in the 101th century. I personally really like Jason Momoa, though his choice for Duncan Idaho is a bit baffling - in the books he's described as slender and agile, the best fighter around because of tactics and smarts and technique, bot because of strength. He does indeed fight like that, and Momoa somehow even sells it, but I don't quite understand why you'd cast someone so muscled to then mostly hide it.
All of the major characters' actors perform really well, in my mind. Some don't get a lot to work with (Tufir Hawat and Gurney Halleck, like in the 1982 movie, are mostly there to tick off their name from the list...But their characters simply don't do much in the first book, either, they're only made ever more important looking back in later books and the prequels), but really, everyone acts well. I was hesitant about Rebecca Ferguson as Lady Jessica but she won me over. Timotée Chalamet as Paul is a really good choice. He's presented as a slender 17-year old in the books, that most people tend to think of him as bigger and stronger is because, well, people like to think of heroes and big and strong 25 year old guys. He's not, and he really brings the character to life. Perhaps the weakest acting of the major players comes from the Duke.
Anyway, good-to-stellar performances by everyone.
Moving on....
Something that concerned me in the trailers were the still suits - open faces, just a small tube in the nose. In the movie, pretty much all Fremen consistently wear their face covers all the time, it's just the main characters who have the face mask down to talk. It's a necessity to see facial expressions and emotions, but I think it's handled fairly well. In some other versions it was presented as if everyone just had a little tube running to heir nose, now it's shown to be more in the background and we're just expected to look past it. I personally prefer it that way, others might disagree.
Some stylistic choices are a bit weird. Why an ornithopter suddenly flies like a dragonfly instead of a bird (you know, orni- and all that), don't ask me - it makes for nice visuals, but it's just as technically stupid. Why the Atreides crest has changed from a stylized eagle head to something I can barely recognize? Not a clue. Are the eyes blue enough? They're not as blue as they're described in the books, but, again, that's a choice to keep acting and facial expressions possible. These are the sort of things that might bother me...If the movie hadn't sucked me in in other ways. Which it does.
Some other choices really do work as I imagine them to. Shields, fighting styles, etc do follow the books quite closely. The Bene Gesserit portrayal as well.
The cinematography and visuals are great. Most stylistic choices really work well and show Villeneuve or the art department or whoever made the choices really understood the material they were working with. The atmosphere works and the difference between the different planets is clear (with a bit of overuse of the orange/blue filters, possibly, but...well, you've got a desert planet and a water planet, what are you going to do?).
The story isn't rushed. It's about 2h30 of movie, and still many scenes have been cut or adapted to shorten them, combined together, etc. Some characters get reduced to nearly nothing (poor Shadout Mapes...And, again, Gurney might as well not be here) but they managed not to make an incoherent mess - instead, the time is taken to allow quiet moments between action and let characters reflect and the visuals to speak. I don't think a single thing is incomprehensible to people haven't read the books.
Somehow this sounds more critical than I want it to be. The cinematography, the visuals, the soundscape, the acting, the style, the pacing, it all helped to draw me in and keep me locked into the movie. I've seen plenty of comparisons to Star Wars, of course, but it actually felt much closer to Lawrence of Arabia for me. This movie tries to find a balance between being thoughtful and visually impressive and an action spectacle...I don't think this will have the mass appeal of Star Wars (let alone modern-day SW), it's too slow and expansive for that, more "old school Star Trek" than "modern scifi", but it's easily the best movie (for my type of person) that I've seen all year.