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Bubbles, unless it's a game that features Michael Jackon's monkey, are not in iOS as far as I know. You can't change icons. Apps can change them though, but it's not like they change them in to something completely different causing confusion for the user.
Folders are in iOS, but they are optional. You don't have to acquire this skill to operate an iOS device.
I have a lot of experience using Palm and iOS devices. On the easy-to-hard scale of usability I would rate them very close to each other, but to me the iOS screen looks more simple.
If you have learned to use one I'm pretty sure you have no problem using the other. iOS does have more things you can do, most not mandatory to use the device, but they are easily learned.