YMMV / God-Emperor of Dune

• Badass Decay:
  • The Museum Fremen are noted in-universe to be vastly inferior to the original Fremen. They know Fremen culture only by rote and make basic mistakes that would lead to a quick death in the desert, are mentioned as often having no idea what much of the Fremen language means and mispronounce much of it, and are constantly petitioning Leto for changes in their lifestyle, despite the Museum Fremen being created for the sole purpose of preserving Fremen culture.
  • The original Duncan Idaho was among the universe's most deadly fighters. In this book, however, his current ghola is shocked to discover that over the past 3500 years, humanity has evolved (and improved) so much that even the relatively unimpressive Moneo is able to outfight him easily. Duncan later learns that Moneo is not even among the real badasses of this era.
• Big-Lipped Alligator Moment: Nayla having an orgasm while watching Duncan climb up a rock wall. While it's made clear previously that she has the hots for him, this particular instance feels unexplained and quite out-of-character (really, solely by watching him climb up a rock wall?) and leads to nothing afterwards.
• Fair for Its Day: Duncan Idaho says some shockingly homophobic things that definitely echo Frank Herbert’s own views on the subject (Duncan is outright disgusted that the Fish Speakers are lesbians). But despite that, they’re portrayed as a relic of the era when the original Duncan lived, with the present view being that same-sex relationships are unusual but nothing to get upset about.
• It Was His Sled: Leto II turning into a giant worm-man hybrid is basically the main thing people know about this book, thanks to Memetic Mutation. It was actually a Shocking Moment at the time.
• Narm: Nayla's aforementioned orgasm from watching Duncan climb a wall.
• Values Dissonance: Some of the discussion of gender roles and differences have aged very badly.
• Values Resonance: On the other hand, much of Leto's musings on the nature of politics and government are still very applicable to the 2020s, 40 years after the publication of the book, and it's likely they will not stop being so anytime soon.