Dune is one of my all-time favorites. So I am a bit biased. However Herbert, like Tolkien, he's not for everyone. I hardly recommend Dune to people anymore because I think a lot of modern readers do not like the pacing or the monologuing. There's not much action compared to a lot of modern sci-fi but the message of rebellion and the jihad I think is very poignant given the current world conditions. I think the theme is still timeless in Dune and very appros of current conditions.
I picked it up as a reread after I finished To Sleep In A Sea Of Stars by Christopher Poalini (author of Eragon).
I am enjoying my reread of Dune. I've been reading a lot of cinematic fiction, space opera (which was TSiaSoS), and epic fantasy lately. The toned-town pace and slow build to turns and moments has me really into it right now.
After I finish, I'm off to An Absolutely Remarkable thing and then I am diving into the new Chuck Palahniuk novel that came out in September (the Invention of Sound) which sounds like a return to form for him. I really enjoyed his first 5 or so books (Survivor and Invisible Monsters being my favorites), didn't really dig his experimental phase, and wasn't a fan of either Fight Club sequels he did so hearing this is more like Choke, Lullaby, Survivor, Fight Club, and Invisible Monsters makes me happy.
Okay side-track aside now ... the world building in TSiaSoS made me really want to reread Dune and compare them. So this reread has been largely focused on the religions and world building (I'm using the map more to see how it works) but the pace has been nice for me. Herbert, like Tolkien, is a great study for world building. A lot of the beats of Star Wars come from Dune, which is why I think Dune is a great place to learn some builds if you're wanting to get into the literary side of sci-fi.
What frustrated you and why were you glad you read it?