In my opinion, it's a combination of a bunch of little things that make the iPhone, and iOS in general, such a good user experience. What are your favorite little things about the iPhone (or iOS) that you've noticed? I'll start. I love how it handles incoming calls while listening to music. Especially when you are using the provided headphones. The music fades out, the phone rings, you click the headphones to answer and just start talking. When the call ends, you hear a little tone signaling that the call has ended, and the music fades back in. You don't even have to press anything. I'm not sure how Android handles this situation, but I can't imagine it would be any smoother than that.