I use Smart Objects extensively as I edit photos, since it gives an incredible degree of flexibility. Smart filters mean that I can always go back and don’t damage the pixels in my images.
Smart Objects is one of the many Photoshop desktop features that is not yet in the iPad version. But if you tap New and Upcoming Features on the Photoshop home screen, in the What’s Coming section it tells you that Smart Objects is one of the features they are working on. We do not know when that will be released, but at least we know it’s on their list.