I find that expecting a twist lowers the enjoyment. The twist, when it arrives, tends to usually be anticlimatic. If it turns out there's no twist, it ruins the whole experience.

I think that's why Shyamalan's later movies are considered so badly.

The "prediction error" point is interesting; I feel cheated when the twist is not so much a twist but hidden information; when one could never have suspected of the truth because not all facts where given. For example, I found the ending of the movie Number 23 to ruin the movie for me, so frustrating it was.

On the other hand, when it makes perfect sense, and facts were there all along, the twist is satisfying. That's why Sixth Sense is so popular.

Also, spoilers aren't always about twists. Telling me the whole plot of a movie robs me the experience of discovering it as it goes. Some of movies I enjoyed watching the most were ones I went in knowing absolutely nothing of what it was about (also some of the ones I disliked the most, but that's another story).