Like God Emperor Of Dune, this book is full of the main character philosphising, which is ironic given that she's a Bene Gesserit and they're supposed to be against that kind of thing. The book would probably have been better at a third of the length. I also wondered why the Bene Gesserit with all their resources, including Other Memory going back millennia, were so dependent on two men, Bashar Miles Teg and Duncan Idaho, to defeat the Honored Matres (and they fail at that anyway due to the Honored Matres use of superior technology).
I was surprised that in Heretics of Dune and Chapterhouse Dune, technology seems to have degraded to the point that most people on Gammu would find the 1980s hi-tech.

If only there was a proper sequel, dealing with such details of the perfect Face Dancers who don't need Masters, or described what is going on in The Scattering. What was the original point of The Handlers and the Futars? Why did no-one think to take some sandtrout from Dune when they joined The Scattering? Why did the Scattered Tleilaxu not use axolotl tanks to make Melange, which would have meant the Honores Matres could have used Spice rather than their adrenalin-based drug?