Boomtown has a solid preview up based on their GC 07 viewing of The Witcher:
An important part of the “monster hunter” game is bound to be the fights. But also here The Witcher distinguishes itself. In more traditional role-playing games (without turn-based combat) the fights often consists of “click-your-opponent-and-wait – repeat-until-he-is-dead”. But in The Witcher, besides the tactical elements such as steel versus silver weapons, use of magic/alchemy and the option to chose between fast (but weak) or slow (but strong) attacks, you have the ability to combine attacks (or more accurately strengthen them) by clicking the mouse at certain times. This should prevent fights from being one big mess of clicking. At the same time, a very extensive skill-tree makes it possible to make many different versions of Geralt, with emphasis on the person you like to play.