It's interesting because it took my boss 2 errors before finding the correct button to reply to an email from his new iPhone 4S. The company gave him a company iPhone, and it's really the first time he had used one. His previous phone was an Android.
1. First time, he pressed the "new message" button
2. Second time, he pressed the "refresh for new email" button
3. Third time, he pressed the correct "reply" button
It shows that a lot of thing we use are as "intuitive" as we think. We have learned it one way or another previously. Years from now, we would think what we thought as intuitive was because we learned years ago. Of course, he now remembers how to reply an email. Maybe in a few months from now, it becomes "intuitive" for him. Heck, if I didn't tell him that double-tapping on the home button will bring up the app switching, then he wouldn't know. Is that intuitive, or is that intuitive only after learning?