I'm an impatient reader. After getting caught up in the story, I want action. The slow build—the long tedious process that takes time and development and careful plot planning—is hard for me. It's not because I have no taste; plenty of classics have slow plots that gradually build and crescendo, then gently decline. The difference? The reader isn't at the mercy of the author; he is learning about the events at the same rate, and the author is just along for the ride. It's as if the two of you are watching the same play simultaneously; he is just transcribing the storyline. When the reader feels manipulated, and the author holds back information "just because," the slow build has been misused.
Write suspense into your story; use the slow build, the steady increase, the thrill of discovery—but don't gloat over him when you keep your reader in the dark. It is, after all, his choice to keep reading.