But whose conventions to adopt? With the three platforms mentioned, adopting any 1 of them over the other two will lead to the other 2 having confused users.

But whose conventions to adopt? With the three platforms mentioned, adopting any 1 of them over the other two will lead to the other 2 having confused users. Adopting elements of all of them will create confusion everywhere. I've used all three platforms and developed for 2, the UI is different enough that you really shouldn't mimic one on the other. The best I found was the Windows Phone 7 guidelines which were extremely well thought out and consistent. Would you have me use those on iOS?