For music instruments, multitouch is an amazing revolution. For too long, we've been restricted to either very expensive control surfaces with physical knobs and faders, or software solutions which required a mouse and only let us move one virtual fader or knob at a time.

Now, I can turn a 10" screen into any imaginable control surface, including using all 10 fingers to move multiple objects at the same time. It's heaven. The iPad does what you would have had to spend $thousands for previously in the recording/mixing world.