I forgot to mention the one scene that is The Dead Zone's only mis-step, and it's a biggie.
SPOILER ALERT IF YOU HAVEN'T SEEN THE FILM
Most everything in The Dead Zone is seen from the perspective of the film's protagonist, Johnny Smith. I'd have to back and watch with that in mind, but I think I'm right - there is only one scene in the film that departs from that - and it's the mis-step I speak of. It's the scene where Martin Sheen as Senator-wannabe Greg Stillson, and his henchman pay a visit to a newspaper man - it shows Stillson to be an evil sob. The scene is bad, and it tips the hand of Stillson long before it should (without the scene, the moment where Johnny shakes his hand and sees the future would be far more shocking and surprising). The scene doesn't really hurt the film as a whole, but if you just skip past it, the film works so much better.