Impressions from someone who almost has the book memorized:
1. The casting was every bit as good as I'd hoped.
2. It looks like they may keep Idaho alive longer. Beast Rabban may have a larger role.
3. I really like the way they're making Paul's "terrible purpose" clearer. I think for a movie adaptation that's a super good idea, and to me bodes well for how they handle the story.
4. That said, the bit at the end suggesting Paul can control the sandworms is ... oof. I hope that's either a dream or just done for visuals.
5. The tiny bit of fight scene between Paul and Gurney was appropriately bad ass.
6. It's interesting what they didn't show. Almost nothing of the Baron (but the little bit I saw fits with #1 above), nothing whatsoever of Stilgar or Thufir Hawat that I noticed. Some of that may also be the result of splitting the first book into two movies.
7. The visual design nails it.