By "classic sci fi" do you mean cheap, badly planned, and completely inconsistent with the works its based on? Yeah...I read Butlerian Jihad...and I wish to god that I hadn't. As far as I'm concerned there's only six Dune books...maybe seven if you count the Dune Encyclopedia (which I think is a hell of a lot closer to Dune canon than anything put out by Herbert's kid and Kevin Anderson. To me, classic sci fi is the orginal Dune, Asimov's Foundation, and Well's War of the Worlds.
That said, I concede that there are some decent parts. I did enjoy the parts that dealt with the Fremen quite a bit. In fact, the Fremen parts are the only sections of BJ that I consider worthy. I wish they could make a book with only those parts in it. There's just enough there for a decent novel. I also enjoyed the character of Erasmus but not enough to like how machines were used in the story. Pretty much all else was poop. The events of the Battle of Corrin particularly pissed me off. It was like the cherry on top of the pie. Only in this case it was cowpie.
Yes...I'm a rabid Talifan.