Of course, surprises come in both big and small varieties. No matter how well you might know Star Wars: The Old Republic's quests, for example, you might avoid looking up all of the datacrons and thus get a pleasant surprise when you find one. Or maybe you don't like knowing about the bosses you'll fight in a dungeon until you get into the fight.
We all like discovering things, but what we like to discover varies. So what about you? How important is having surprises in a game for you? Do you like to walk in with as little foreknowledge as possible, or do you like to have a pretty good map in your head before you start playing?