I'll start with the negatives so I can end on a positive note.
This movie was stunning... but a bit confusing at times for people who haven't read the book. That's mostly why I give it three stars; some of my family members had no idea what was going on. The movie could have explained itself a bit better for newbies going into it.
As beautiful as this movie is, it drags on and on and on. It truly is a spectacle to look at, but at times that's all it is; scenery. No story, just people walking through the desert. It can be a bit boring at times.
I also don't think this movie is quite as awesome as people say. Yes, it's great fun, but it's no Lord of the Rings as many have claimed. Hans Zimmer's score was mediocre, and I was a bit disappointed in it. The pacing was off at times, and the acting was sometimes dull.
BUT for the positive stuff...
For the most part, I really really enjoyed this movie. It was incredible to look at. The scenery was gorgeous and I watched a behind the scenes video on the movie... apparently they use very little CGI and a ton of practical effects, which makes it more enjoyable to know how much work was put into it. The movie stuck very close to the book, which I definitely appreciated. The costume designs were spectacular, and the actors and actresses themselves all looked gorgeous (especially dear Timothée). There were many scenes that gave me goosebumps and made me feel a sense of awe, especially the scenes with the sandworms.
Overall I give this film a 3/5. It's a beautiful movie, but it can take itself too seriously and it tends to drag on a bit. However, I still really enjoyed it and I realize it's "Only the beginning" as Chani said. Definitely interested in the next installment.