My son Roman is 11 months old. In my efforts to keep him entertained in the mornings while mom is trying to catch a few extra winks, I will occasionally let him toy with my iTouch. He very quickly picked up the swipe and flow interaction of the UI. He also very quickly figured out the function of the main button.
Obviously I’m impressed with the little guy for figuring this out at such a young age. But I can’t help but be impressed with Apple as well. After doing a little poking around on YouTube, I found that there are many videos of toddlers with their parents iPhones. Kudos to the UI team at Apple.