In usability tests you'll see that pinch-to-zoom is hardly discoverable, or even particularly easy. It's a learned behavior.
Once users "get it", it's powerful. They'll attempt to pinch to zoom all over the place. I guess I don't see how this is any different. It's a gesture, and I find it to be intuitive (it's been available on the Android version for a really long time).
Apple has been teaching gestures to people through marketing. I always thought that was brilliant. Gestures are not at all discoverable, but if you show them often enough they become natural. Most of Apple's TV ads, especially those for iOS devices, are little tutorials.
It is, however, a bad idea to rely on that. I see gestures as I see keyboard shortcuts: not intuitive at all, but potentially great time savers once you learned them.
For those making touch UIs this means, quite simply, that you always have to be able to do something without gestures or that if a gesture is essential, it has to be taught to you.
I agree. The intuitive way to zoom in is to move your face closer to the screen. Pinching a screen makes absolutely no intuitive sense. People learned it by accident or because they were shown.
Test I've previously conducted as part of product development. I've, anecdotally, have heard similar reports from others as well when we've shared data.
Are you sure your two year old didn't watch you first?
My 18 month old niece was the same with my brother's iPad, being able to navigate back to the home screen, find the YouTube app, go to history, watch something from the list, full screen, rewind and go back to the history once the video had finished. She has now picked up using Android on Samsung Note II pretty kid. Kids are just really intuitive and learn very quickly by watching at that age, I was truly amazed since my 60 year old parents on the other end of the spectrum have great difficulty understanding this tech.
Once users "get it", it's powerful. They'll attempt to pinch to zoom all over the place. I guess I don't see how this is any different. It's a gesture, and I find it to be intuitive (it's been available on the Android version for a really long time).