The latest Game Informer has a feature about Rock Band, with mockups of the controllers. Or, rather, pictures of a microphone and a Fender Stratocaster, and a mockup of the drum kit. The image may or may not resemble the final drum kit, depending on whether or not Harmonix changes the prototype and on whether or not the Game Informer team has learned the secrets of Mega Memory.
According to the caption, "This isn't an exact representation of the drum kit -- Harmonix should reveal the final design soon. We crafted this picture from memory based on the time we played with the prototype." It's got everything we need: stuff to hit and stuff to kick.