One of the cool features of Ipad Garageband is the keyboard which allows you to add some cool expression to your playing by selecting the PITCH keyboard mode which allows you to slide your fingers up and down the keys to change pitch! Wouldn't it be cool if a real keyboard would allow this!!
Give it a try!
My next thing to try is importing from mac to ipad and back again to add these expressive keyboard parts to my mac garageband parts!