I liked my prof's approach to exams:

"You may bring one 8.5x11 double-sided cheat sheet into the exam. You may write anything you want on it. And I promise you that if you prepare such a sheet, you'll never even look at it during the exam."

And he was right.

I certainly find that now, going back to uni. In a couple of subjects we get the option to prepare a cheat sheet, and I would say I actually look at less than 10% of it. The act of preparing it forces me to revise, and internalise the facts and ideas.