Thanks to IGN, we now have a real credible source demonstrating the size of the Revolution's free-hand controller. As you can see in the picture, the GameCube controller's relatively modest size absolutely dwarfs the Revolution controller.

For some reason I always assumed it was a big larger--at least lengthwise--than the Gamecube controller, but it seems to be about the same size as the Xbox 360's mini media remote. This is important because if you're holding the controller in one hand, you have to be able to reach all the buttons easily, which can only be done with a small remote. Thanks IGN!