iChat shows a mirror image of the video feed so that then live picture that you see looks natural, like the image you would see in a mirror. So if you wave your right hand, the hand on the right of the screen will wave. I think this is reversed back to normal for the person you are chatting with so they see you as if they were behind the camera looking at you.
iMovie should just treat the video feed as normal, as if the viewer was behind the camera.
Its a neat trick in iChat as its wierd watching a proper live picture of yourself.
