Quite early on in the game you get to make an interesting decision and it makes Witcher's design philosopy shine. It is very early on, but mentions a repercussion later in the game, so I will cloak it: You are asked to help a trader, who stocks his goods at a river, to get rid of some monsters for him, who come by at night. You go out at midnight, do that, and as soon as you have killed the last one, a group of elves comes by and demands their goods. It is unclear if this is an actual agreement between them and the trader or if they try to steal. Elves in the game are harassed by humans to the point of driving them to extinction. Anyhow, you can now decide if you let them have the wares or not. In the latter case you have to fight them. Quite a while later in the game, two things can happen, depending on how you decided: If you let them have the wares they kill a person you need to get information from. If you killed the elves, later on another elf will be killed by humans, because evidence found on the bodies you left leads to him. And you'd need that elf, too to get information.
That your decisions within the game matter, is really nice.