Well, there's me...
Although I think the Dragonrider series peaked with "The White Dragon," all the books have been worth reading. Okay, I never managed to finish "Masterharper of Pern." The brainship series was good, although again the earlier stories were best. Please don't bring up "Acorna."
It must be extraordinarily difficult to carry a group of characters and a situation through dozens of books and try to keep it fresh. Given the work I'm going through on one book, a sequel would kill me. I have my doubts that the seventh Harry Potter book is going to be that good.