I continued to be amazed by how user friendly iPhone is. Yifan loves to play withy iPhone. His current favorite is to long press the icons on the home screen and rearrange it.
If turned our that everyday, when I want toake a phone call or send an SMS, i found the icons are rearranged so I need to solve a small puzzle to find it either in another screen or hidden in another folder.
That always put a smile on my face.