I wouldn't exactly worry that it gives players narrative control, though – it only gives them control over their own characters. A player can say "I stab the bad guy in the face" and that will happen, but he can't control how the bad guy reacts or even if the blow seriously hurts him (in a scene-affecting way).

Players can't control the plot outside the actions of their own characters, which is the same as always. They just have much more control over the aspects of their characters' lives that were previously mediated by dice. It takes very little control away from the DM.