I agree with this for some of his work, and IT in particular. The ending, from what I remember, killed it.
(SPOILER)Where the clown turns out to be some weird spider-alien that's projecting images into their mind? What? It would have been so much scarier just leaving it as what everyone assumed it was, a horrible demonic clown creature. I think I enjoy Cujo a good bit because it avoided that kind of weird ending, and just stayed true all the way through. It was a sad book, but that's what made it good.
I actually like the slower pacing a lot of his books take, and I like the time he takes to describe more mundane aspects of everyday life and the small towns most of the stories take place in. A lot of people don't like it though.
I need to go back and read Firestarter.